Why do people own multiple (10+) horses on farms?

A few months ago, I was driving around outside of Calgary and I noticed tons of farms had several horses. When I used to ride, I stabled my horse at a facility, but it was pretty small (maybe 8-10 horses when full), and it was a riding/training facility, not a farm. I've seen these farms full of horses a lot, but never really thought about it until a few months back.

Why do people have so many horses? I can't think of an agricultural purpose (except for grazing, but goats seem like a much cheaper alternative for that.)

Are these large stables for personal owners or something?