Having looked into this a bit, I have some hints for an answer. I'm still not convinced I understand the full mechanism, so any feedback is welcome here.
I think some of my sources might be paywalled; apologies for anyone unable to access them.
Reading a few studies on the effects of different variables on the outcome of deep frying (specifically potato ...
Firstly, I would challenge both of your assumptions.
(a) dripping doesn't go off
Like any other fat, lamb drippings can and will go rancid over time.
(b) any germs/bacteria would be killed by the heat of frying
While it's true that any molds or bacteria themselves will be killed by heat, the same does not hold for any toxins they may have produced.
I have an All Clad SS pan, a non stick pan, a lodge cast iron and I have fried an egg with a small amount of butter on low heat and the egg does not stick.
It slides around the pan more easily than any other pan.