system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are cats obsessed with boxes?

I've even seen large cats (tigers, lions) enthralled by them.
gpt
A lot of 'solitary predator' animals (as opposed to *group/pack* predators, like dogs) feel safe in more confined spaces, like boxes and small caves. It's part of their survival instinct -- if you're surrounded on three sides, then you know you're safe there, and you only have to pay attention to what's in front of you, because it's impossible for anything to sneak up on you from behind. If your body is taking up the entire cave/box/etc, then there's nothing else in there with you, so it's even safer.

Housecats don't have the sharpest survival instincts, but they've retained that sense of feeling safe and comfortable in boxes and little nooks and crannies.

It doesn't usually happen with dogs, because dogs are pack animals -- they get their safety from hanging around in their pack, and aren't as careful about being hidden.