In the US, bicycles rarely serve the purpose of transportation. Kids think of bicycles as toys, adolescens want cars as soon as they are legal to drive; most people never know, or even think about how far they could travel on their own physical ability.
As a former bicycle shop worker, I’ve seen kids come into the store wearing $200 sneakers.. but parents too cheap to buy a $35 helmet.
For a 17 year old, I recommend riding a bicycle, regardless of their physical fitness. the experience a 17 ear old can gain from riding a bicycle around is worth far more than most could imagine. More than likely, a 17 year old with cycling experience would become a better, more understnding motorist toward other occupant of the road like cyclists or motorcyclists.
Grow some skin, this is the internet, people are wrong all the time.