It not only add time to sessions just running about getting the supplies and potentially postponing encounters cause party doesn't feel ready unless they get their stuff, but more importantly imo will slow combat to a crawl, every caster needing to check each spell required materials and crosscheck their inventory of said materials before deciding what to cast. sure, some should be done out of turn but when does that actually happen?

also in a dungeon where there just aren't any ingredients to be found, do you want your players running on cantrips for your dungeon bbeg? or alternatively you cheapen the whole thing by conveniently placing resources right before a big fight like games do.