I am living in Germany and know at least 2 people that do it. But why would you take the risk if you could just buy very good beer at your local stores?
Some people do it as a pleasurable hobby. You might also ask why someone would build furniture if they could buy it, or why they play a musical instrument if they can just listen to the radio.
You may like a particular style of beer that isn't popular. And, especially in Germany, you may want to make a style of beer that you can't buy in the store - one that has other flavor ingredients, so it doesn't comply with the beer purity laws.
Hello from the homebrew community. There are many reasons to brew yourself, and the first reason is because you can. This question is the same as "why bake your own bread?", "why grow your own food?", "why start your own business?" Because you can!
There is something primal and fundamentally connected to nature about brewing, and being able to harness a fungus to produce alcohol. Not only this, but something spectacularly human about being able to produce something by yourself, and brewing beer and wine is surprisingly easy. Consider that you then get to drink something you made and the satisfaction of being self-reliant in this respect.
The satisfaction of self-improvement and being able to share your creations with others can't be put into words. You most certainly can buy beer, but you absolutely can't buy the beer I make. Also, mine costs a fraction of the price that you pay others to make for you.
I hope I have answered your question. We brew because we can, because yeast is freely available to all, and because it improves our skills and human capital. Most of all, just like any trade, whether it be a carpenter, a butcher, or a chef.... we get to enjoy the fruits of our labour of love.
Because its a lot of fun! I always feel like a mad scientist when I'm boiling up the wort on the stove adding ingredients, especially when adding the hops. Its quite amazing to watch the yeast consuming the sugars and making the alcohol, yes you can see it!
Homebrew is healthy for you. It is a living beverage. All the yeast, enzymes and vitamins are all there for you just like nature intended. Large commercial brewers filter most of this out and some even have to add back in the carbonation.
Homebrew is not dangerous, the worst that will happen is bacteria will spoil the beer's taste. There is no documented case of contaminated beer that has killed anyone. The theory is since the yeast micro-organism already 'lives' in the beer they create an environment that is not favorable to other micro-organisms.
Finally if you are not old enough to buy alcohol, usually you can buy the ingredients and make it yourself. The brew shop I frequent is very close to a large college campus. Coincidence? I think not.
It's exactly as with food.
By cooking* at home, my wife and I can always get the food** that we want, exactly the way we want it. There is a chance of us screwing up and ending up with bad food**, but with practice that doesn't happen very often. There is some food** that we are not well equipped or trained to make, but that we happily buy from professionals. And it's cheaper to do your own cooking* than to buy everything ready-made, if you discount the cost of labour and appliances.
If you want to exclusively have food** that someone else makes, that's your choice, and modern society can provide. But I think cooking* at home really is rather sensible.
You ask a great question. I think a great reason to do it is to learn. I like the answer 'Personal Taste' above. If you already know what you like you can make it. But, if you're just playing around brewing you can come up with tastes you never thought of. You might even like your own recipe.