almost all the kinds of fake salad I can think of have mayo as a main component (and i know my fake salads)
macaroni salad, potato salad, broccoli salad, tuna salad, chicken salad , jello salad (yes me too i'm also retching thinking about this), cabbage salad (i mean, erm, coleslaw)
on one hand it's a binding agent
primary alternative/substitute for this generally seems to be a vinaigrette dressing (german potato salad, idk what else)
on the other hand i guess the requirement for a dish to be a salad is that it has to have some kind of dressing and that's about all it takes to qualify. which is not really what the average person thinks of when they think of 'salad'
and now i've written salad way too many times and it doesn't look like a word to me anymore.