I mean, feet and armpits smell, but that's a different type of smell from farts:
--> Feet, armpits (and sweat on other parts of skin) have a smell coming from isovaleric acid - produced when skin bacteria (mostly Staphylococcus epidermidis) metabolise our sweat.
It can actually be enjoyable, but as an addition to the look of these parts of body.
--> Farts, on the other hand, mostly smell like ammonia. We actually can like the smell of our farts, because we know it comes from our body and is not a foreign substance. However, we dislike someone else's farts, because I guess our brain suspects them as some sort of toxin.
This implies, that it is more natural to enjoy feet smell, than fart smell in physiological perspective.