Why do you call some wines by region and other wines by grapes varietal? What is the reason behind?
This is a historical thing. In Europe in the ye olden days, there was no separation between where someone grew the grapes and what the wine was called, ie Burgundy, Chianti, Bordeaux, Rioja. In most of these regions, these grapes were selected over generations of growers to work perfectly in those regions.
Later on, maybe about 100 years ago, people started naming their wines similar names to these well known regions. Champagne is the classic example and probably the first to assert it's region name (aka appellation) around the world. Calling something Champagne in California did not make it Champagne. Champagne only comes from the Champagne region of France not Napa Valley in California.
It was intrinsically known what would grow where in Europe and mostly people didn't fiddle with it. Chardonnay and Pinot Noir grew well in Burgundy and that's pretty much all they grew. Then along came the New World. Mostly after WWII, growing regions all over the world started growing grapes and didn't have the history that many of these old European regions had and they wanted to tell people what was in the bottle so the rise of grape names came into being.
In Europe they created governing bodies to protect their appellations and making laws about how and what people could grow grapes. Protecting place names became a big deal. Now it's spread to many other things like tea, cheese, tomatoes (San Marzano), etc.
In the new world, they have the freedom to pretty much grow whatever they want, how they want and wherever they can so an emphasis on cute names and grape names is emphasis and places where grapes are grown are de-emphasized (OK, there are excepts like Napa Valley and Barossa Valley) As new world areas really figure out what is best grown in their regions you will see more emphasis on regional names and less on grapes.
It depends on the wine.
If you have a quality assurance label, and a strong relation between a particular region and a kind of wine, it's better to call wines by region.
The same is true if you can get different wines in different regions from the same grape varietal.
Also, if the wine is made from different grape varietals, calling by region is an obvious choice.
Just thing about Champagne and Franciacorta: they are well-known regions for sparkling wines, the wines are from mixed grapes, and the grapes are "almost" the same.
Why do you call some wines by region and other wines by grapes varietal?
There are several factors to be taken into consideration here. First of all, let us start with the definition of what a grape varietal is.
A varietal wine is a wine made primarily from a single named grape variety, and which typically displays the name of that variety on the wine label. Examples of grape varieties commonly used in varietal wines are Cabernet Sauvignon, Chardonnay and Merlot. Wines that display the name of two or more varieties on their label, such as a Chardonnay-Viognier, are blends and not varietal wines. The term is frequently misused in place of vine variety; the term variety refers to the vine or grape while varietal refers to the wine produced by a variety.
As vintners and consumers have become aware of the characteristics of individual varieties of wine grapes, wines have also come to be identified by varietal names.
The term was popularized in the US by Maynard Amerine at the University of California, Davis after Prohibition seeking to encourage growers to choose optimal vine varieties, and later promoted by Frank Schoonmaker in the 1950s and 1960s, ultimately becoming widespread during the California wine boom of the 1970s. Varietal wines are commonly associated with New World wines in general, but there is also a long-standing tradition of varietal labelling in Germany and other German-influenced wine regions including Austria, Alsace, and the Czech Republic. - Varietal
Wine region as such generally are those regions which have had some amount of known historical wine making in their past and thus are more well know as such.
The usage of these terms seems to have several factors involved in why we call them as such.
Unlike American wines, most European wines are named for the region where their grapes grow rather than for the grape variety itself. Many of these European wines come from precisely the same grape varieties as American wines (like Chardonnay, Cabernet Sauvignon, Sauvignon Blanc, and so on), but they don’t say so on the label. Instead, the labels say Burgundy, Bordeaux, Sancerre, and so on: the place where those grapes grow.
Why name a wine after a place?
Grapes, the raw material of wine, have to grow somewhere. Depending on the type of soil, the amount of sunshine and rain, and the many other characteristics that each somewhere has, the grapes will turn out differently. If the grapes are different, the wine is different. Each wine, therefore, reflects the place where its grapes grow.
In Europe, grape growers/winemakers have had centuries to figure out which grapes grow best where. They’ve identified most of these grape-location matchups and codified them into regulations. Therefore, the name of a place where grapes are grown in Europe automatically connotes the grape (or grapes) used to make the wine of that place. The label on the bottle usually doesn’t tell you the grape (or grapes), though.
The terroir game
*Terroir is a French word that has no direct translation in English, so wine people just use the French word, for expediency. Terroir has no fixed definition; it’s a concept, and people tend to define it more broadly or more narrowly to suit their own needs. The word itself is based on the French word terre, which means soil; so some people define terroir as, simply, dirt.
But terroir is really much more complex (and complicated) than just dirt. Terroir is the combination of immutable natural factors — such as topsoil, subsoil, climate (patterns of sun, rain, wind, and so on), the slope of the hill, and altitude — that a particular vineyard site has. Chances are that no two vineyards in the entire world have precisely the same combination of these factors. So terroir is considered to be the unique combination of natural factors that a particular vineyard site has.
Terroir is the guiding principle behind the European concept that wines should be named after the place they come from. The thinking goes like this: The name of the place connotes which grapes were used to make the wine of that place (because the grapes are set by regulations), and the place influences the character of those grapes in its own unique way.
Therefore, the most accurate name that a wine can have is the name of the place where its grapes grew. It’s not some nefarious plot; it’s just a whole different way of looking at things. Understanding Wine Names by Region