OP, you have lots of valuable horse experience but only in a limited slice of the horse world. You have been watching the worst possible peers for your peace of mind and self esteem: juniors with well-off parents. The kids don’t need to have jobs, just ride, and they don’t really know the cost of anything.
Realize that’s a bit of a bubble. All those kids are also going off to college, and most will give up riding for the college years. If they return as adults they will need to balance busy careers, motherhood, and general adult life with riding. They will be in the Catch 22 situation of needing a “big” career to fund the horse if they want to stay in H/j but not having the time to devote to riding that they had at 15.
”‹”‹As far as career, I find a lot of young people understandably only know about the jobs categories they’ve observed in daily life. Nurse, doctor, teacher, dentist, vet, fireman, policeman :).
There are so many more jobs out there! If you have the science ability to do well in pre-vet you are admirably placed to do a huge range of jobs in research, health care, government, etc.
Just remember that anything to do with people pays way way more than anything to do with animals. And that by and large there is more money looking after small animals (especially dogs) than farm animals (including horses).
I would say pursue your science courses but also keep an eye out for other career paths. You might find something unrelated to horses that fascinates you and pays well.
It is not a bad thing at all to have horses be an entirely amateur part of your life, to be the bill payer and not need to have to earn money at the expense of horses.