I worked at KFC as a teenager and it was very clean as well. If I was on an opening crew in a Saturday or Sunday morning, we spent an hour cleaning and disinfecting everything - counters, floors, grills, tables, etc. before we opened the store. The milkshake machines were washed/sanitized daily and the soft drink dispensers were thoroughly cleaned three times a week.
Not sure what it’s like these days.
I spent years working in restaurants and fast food around the country, and the fast food chains were all stainless, shiny, and constantly cleaned, and like you said sterilizing was a real part of working there, not just wiping something down but actually disinfecting it.
A lot of regular restaurants were clean for the building type and age and some were downright disgusting, since then I have been in the back of many an immigrant owned restaurant and my impression is that they are graded on a curve, a big ignoring curve.