This has not been my experience for the vast majority of non-foot fetishist. I have certainly met those that find feet gross, but most seem more indifferent. It usually stands out to me as an oddity when someone is actually repulsed by feet. This may just be one of those subcultural things where there are some regions where that kind of becomes the norm. Not sure!
Historically, however, feet have been treated as repulsive or dirty...largely because they were. Good footwear, hygiene and sanitation are unfortunately relatively recent innovations. For most of the time humans have existed, one of the least hygienic, most disease prone parts of the body were the feet. There may be some genetically encoded (or even educationally passed down) behavior that still manifests in some people because of that–I don't know. But I think that history probably has at least something to do with some people's seemingly innate interest in feet. For most of human history, if a potential mate had bad feet, they might not survive, or at the very least might end up as a burden impacting the other's ability to thrive.
Those are just some thoughts–again, I don't really know. It would be interesting to have real data from different regions of the US and the world for how many people are repulsed by feet.