They breed like rabbits.
My wife takes care of her grandmother each day for a few hours. There are stray cats there that have been multiplying for the last few years. At one time there were 10+ - and, of course, my wife wants to feed them and take care of them. That gets expensive, especially for cats that won't even let you near them. Thankfully most of them left or got nabbed by a fox or something.
The cat we had that died was great, but in the last 2 years or so had trouble knowing where to crap and she threw up 2-3 times daily - so I'm not pro-cat right now.