If you already own a cat, you probably learned real fast that you’re more of a servant to the cat rather than its owner. If that’s the case, you probably don’t need a single reason to own a cat since your cat already owns you.
However for the rest of the public out there who may not have a cat, you may need a reason to make your life harder than it already is by getting a cat to keep you company. One reason to get a cat is so you can see how relaxed and care-free your cat can be, especially when someone else (you) has to do all the work, pay all the bills, buy all the food, and clean up all the litter boxes in service of the cat. if this is your idea of relaxing, then you probably should get a cat right away.