I don't understand how beer can be sold in a supermarket, yet not be required to have the alcohol content listed on the bottle. This can lead to serious consequences, if the person drinking does not realize the amount. Triple IPAs up to 13%...Not good.
There is no requirement from the TTB at the federal level to include ABV% on beer labels. Individual states can mandate that. Washington state, where I live, mandates that any beer over 6% needs to put it on the label. So, what you end up having is a hodgepodge of different beer labels. Nationally distributed beers usually put it on the label since they don't want to have different labels for each state. Locally made beers in your state may not require it, so that's why you aren't seeing it.