@tripu mostly a feeling thing science types might not get, or people u0se as counter balance to computers and robots which stimulate all but a few things a (and lack of positive humanity overall) with a small mammal (that doesn't talk back) can more-humanly provide some missing things (interaction etc).
I agree on some thing especially in apartments if not outside but as for feelings it's personal thing...
For a bad example much like asking 'why do people play with computers in an apartment mostly' as a kind of different comparison (not serious) but shows how screwed things can be or just for many unsaid purposes or "social' things served (which maybe aren't really in the end).