Kitty seems to be a fairly popular name for cats as well. Half the cats I know are named this. Maybe I just don't know very original people. Our cat was a stray, and the first (only) name it reacted to was Kitty, so it stuck.

Besides the obvious reason for the name, that it refers to a young cat, I've heard that cats actually respond better to the "tee" at the end of it. Particularly if you scream "HERE kittykittykittykitty!!"
That would definitely not work with a name like, say, Ralph.

But above and beyond there's still one name left over
And that is the name that you never will guess
The name that no human research can discover
But THE CAT HIMSELF KNOWS, and will never confess.
— T. S. Eliot