Why do adults keep pets in cages? What type of person derives satisfaction from such an arrangement? Are they just low-empathy individuals?
Of course, it depends on the animal. Highly social animals like guinea pigs may work even with a comparatively small cage, as another member provides sufficient stimuli.
Tarantula -- sure, whatever.
Leon the lobster -- I believe lobster inner life is rather complex for being a sea bug, but again, alright
Small snake or lizard -- starting to get questionable here. The question I would ask myself is: does this species in the wild roam a lot? If yes, then I consider keeping such a reptile borderline mistreatment.
Mouse -- it depends on the size of the cage. If it's just a small desktop cage, then how do people think this is a stimulating life for the mouse?
Tiny bird -- keeping a bird a majority of the day behind bars seems to me extremely immoral, and I'd only consider a (significant fraction of a) room-sized cage proper.
Parrot or other bigger bird -- this is just straight up cruelty. One hour outside the cage a day, if the wagecuck owning this pet didn't have overtime that day, doesn't really make up for the other 23 hours.
Rabbit -- literally why.
In case some of you were dropped on the head as a babby and can't parse my intent: of course my solution is to let the snakes and rats roam liberally inside your apartment, like God intended. No, you dumb frick, I say we just should not keep rats and other such animals as pets, unless we actually have non-trivial means for making their life amenable, like mentioned half-room sized cage.