It depends on what adding fat is.
If I cook a ribeye in bacon drippings, that's OK because a lot of the extra fat stays in the pan and even more is released from the steak. Same with the bacon, that's where I get my cooking fat. The bacon releases the fat and it renders out into the pan.
But, if I decided to drink the fat in the pan, that would be needlessly consuming fat and extra calories for no reason.
I think another problem with too much fat happens with adding fat to coffee for no reason or eating hunks of fat in a fat bomb would also be unnecessary plus it's void of any nutrients.

I remember that Atkins book said that many people begin the diet in a malnourished state and that alone I think can drive a craving for carbs because the body is searching for nourishment, plus the withdrawal from carbs is lurking.
In that case, butter on the veggie needed to make it palatable for many of us and keep us on track with meat and veggies.