There are an unfathomable amount of animals that should not be kept in captivity, much less as pets. Let’s start with the basics—animals that are a danger to basic human life. It’s rare but not unheard of where people will pay large amounts of money to have a pet tiger, a wolf, or even an alligator! This obviously raises a few alarms in your head already, right? For one, all of those animals I just listed could bite your leg clean off. Owners have been mauled to death by their own ‘pets’ due to their own negligence which often gets the animal put down as well. In other scenarios, a lot of animals simply do not respond well to not being in their natural habitat. Exotic birds often get sick and pluck their feathers out due to stress after being caught and sold, and we have only ourselves to blame that hundreds of species of those birds are going extinct.
TL;DR: humans are idiots