AR-10's are good hunting rifles (.308 Winchester, .243 Winchester, 7mm-08, etc.) but are pricey compared to a bolt-action. AR-15's are chambered for low-powered rounds based on the .223 Remington case length, and typically deliver only ~2 kJ or so of energy compared to ~4 kJ for a deer rifle. An AR-15 can kill a deer with careful bullet choice and very careful shot placement, but there isn't as much margin for error, so they are more often used for hunting prairie dogs and other smallish animals, up to coyote-sized.

The vast majority of gun owners are nonhunters, though, and AR-15's absolutely dominate centerfire target shooting in the United States, both competitive and recreational, and are the most popular rifles in U.S. homes. Gun ownership is mostly not about hunting.