Pure curiosity - Does anyone else have different responses to being thanked depending on the type of thing you're being thanked for?
Example - I tend to respond "Of course" if I'm being thanked for something I consider default behavior. The logic being there's no need to welcome, whatever it was is just basic default decency.
"No problem" I usually use for things that somewhat expected. Such as picking up from an activity I participated in.
"You're welcome" is for an actual favor.