Especially since medieval type societies normally had alcohol for all ages at low strength instead of water... Though magic would definitely make the need less, probably they didn't have the same worries we do about driving or the like. ...Magic could also probably cure drunkenness, so probably not as big an issue anyway.
Though I definitely am okay with characters just not liking the taste or state of being drunk. Smell of it makes me sick so I don't drink myself.
That would be understandable. But I'm all these isekai it's always "I can't drink, I'm still a minor!"
Like bitch, in this world you're considered an adult at 15, you've been fighting life am death battles against monsters for years, you received you're own title as a baron with all the responsibilities that come with it, and there are already 2 girls lined up to marry you. You're not a minor in this world, drink the damn alcohol!"
I'm not sure (because I'm not from Japan) but I imagine it has to do with censorship and ratings.
In manga that is supposed to be violent with lots of fighting, there is rarely any gore. Also, there may be suggestive behaviors and appearances but not much (or any) sex.
I know that the behaviors of minors can have an effect on the rating of media where I live.
Underage marriage? No problem. Sending minors on life-threatening missions? Just fine! Making minors take on roles only adults should? Is there a problem? But underage drinking? Nu-uh! Not possible! Big no no!
It's always the same with isekai. I wish these authors would just stop dancing around the alcohol thing so much. The MCs already do tons of things only adults should be doing, what's so different about drinking some alcohol?