Because stuff is moving. Cats love watch things that are moving. Those leaves flying through the air is very interesting to me, thank you.

Being one with the cats, I can tell you that they like seeing things move. Plus, they think that when they take over, you will make a good worker.

Checking out where to find the cleanest litter box.

They are control freaks and have to know where did you change what.

looking for food

in case they find a mouse i guess?