I only stan based on music so I don't think about the age factor. Even my biases are chosen because on how much I like their musical ability.
If someone stanned based on how physically attracted they are to a member and the member was underage, it would be, but otherwise I don't think it's a big deal. People can stan for all kinds of reasons beyond sexual/romantic attraction.
They are more reasonable in pricing for good quality
They also last longer for me, even a lot of waterproof US stuff wipes off after a while. Someone once commented that it's because US buyers see hard to get off products as a negative. 
The only US costmetic item I won't let go is the neutrogena hydro boost hydrating tint (man that took forever to memorize). Everything else are korean/east asian brands.
Sometimes, depends on the activity.
A good amount are bright songs because they just put me in a good mood and help me take my mind off how my body is feeling. Some are just songs that put me in a good mood because I really like them and they aren't too sad.
Here's a couple songs from it:
The stage version during team b days makes me really cry, but the studio version gets me teary eyed as well, typically when B.I comes on and I think about him leaving
stage ver:
Yes
Nope
Big Fish
