[quiescant_dodo]

I'm not sure cats are content with the 4 walls around them, either. (Plenty of cats prefer the outdoors, even if they sleep inside.)

[xkcd-sucks]

Well yeah - What do cats do? Hunt little critters and patrol/defend territory. It is difficult to get suitable environmental enrichment indoors for something that can't read.

[unstatusthequo]

I’ve seen many a cat enjoy cardboard boxes.