FWIW, there are some assumptions made about adulthood that annoy the living shit out of me, such as the cutesy phrase "adult beverages" for booze. I have a hard time expressing how marginalizing it feels to be told, in effect, that because I choose not to drink alcohol, I'm not a REAL adult.

I've always taken that expression to mean "beverages only meant for adults," not "beverages all adults consume." It's the same kind of euphemism as "adult entertainment" - it's not that you're not an adult if you don't partake, it's that if you're not an adult, you shouldn't partake.