I would say they are at least sometimes unnecessary for it, at least insofar as any mechanic is necessary. In the same way we could cops and robbers our way through every TTRPG combat, but don't, because there are interesting situations that come out of being surprised by a tougher-than-usual foe or a stray crit or what have you, the same holds true for the social. Drawing out the surprise and discovery could be natural for a group of roleplayers to the point they play essentially systemless, but that is the exception rather than the norm --- most groups need (if not enjoy) some kind of structure. The question for each game then is, I think, what is the agreed upon structure, what does the table want help with?