Ketchup enhances most things.....

Mayo on fries is like warm potato salad. German in origin and adopted across Europe particularly in Belgium where potato fries were first created.

It is also a very popular way for people in the Southern US to eat fries.

I prefer fries with mayo over any other condiment.

I always say, don’t knock it unless you have tried it.

A lot of opinions here seem to be judge first before trying. I like to do the opposite, try first and then decide if I like it...and don’t judge others that have a different opinion AFTER they have tried it.
I'll try new foods if they look appetizing. IF they don't, they just don't make it in my mouth. Now, for dipping fries in mayo? I'd spare one fry for the tasting.