Although I expect I'd get a bit bored with crushing old horses into those tiny tin cans all the time. Fish are very easy to maintain, and it's possible to develop a very close relationship with them. Sometimes too close. And although it's not against the law to give physical expression to your love for a coy carp, your friends and neighbours may not understand your actions. And the stigma of having a long-term sexual relationship with a goldfish is not easy to shake off.
Some people like to keep livestock.
These people are known as farmers. To tell whether or not you are already a farmer, take a look out of your window. If you can see a large field full of sheep, pigs, chickens and cows, then it's likely that you are. If all you can see is a row of terraced houses, and if you live in a terraced house yourself, then you probably don't keep livestock. Then you're probably breaking a number of environmental health laws and spending all your money on cattle feed.