Partly for the saturated fat, partly for less extreme amounts of omega-6 (though some plant oils are not as bad as others), and partly the personal fact that my stomach doesn't seem to like significant quantities of olive oil, but craves large amounts of animal fat. Whipping cream and butter are both mammal fat that don't require killing the animal - eggs fried in butter are quite tasty :)

I never really monitored the amount of protein I eat, but it has to have gone up. I do eat fatty cuts of meat, but I add a lot of nearly pure fat to my diet, so it's a bit of both.