Because 3.5mm is an already existent audio standard that is not only for cell phones but for sound instruments in general, because all my earphones and earbuds are 3.5mm and because I'd like to listen to music while the phone is plugged in and charging

All of them suck.

3.5 works everywhere else and I prefer my headphones to work with my audio gear. The inflight entertainment on Delta uses 3.5 for example.

Quite a high chance that your phone will also run out of battery on a 12 hour flight.

This is a very funny joke that several people didn't get.