Go figure. I once had a fried egg sandwich that came with mayo at a burger joint, and I couldn't even finish it. I guess that combo just doesn't work for me, despite eggs being a major component of mayo. Buttered toast for my fried egg sandwiches every time.
Until I started posting here, I had no idea anyone would ever think ketchup with eggs was weird or gross. In Chicago, they bring you a bottle of ketchup with your egg order! Well, maybe not in the hipster places, but at plain old diners, sure.
It has a warm spot in my heart but I don't make/eat it. When we were little and we had the rare treat of shrimp cocktail, Mother made them a regular cocktail sauce with horseradish etc. For us, she made "pink sauce" for dipping, a combo of mayo and ketchup.