An interesting obsevation came out of player discussion at my table (PF2e a mechancially heavy game).
Some of the best RP of the campaign so far game from one character depending mechanically on another. Needing a partner for positioning to get flanking. The psychic giving another player an extra strike to finish an enemy. The healer keeping the tank in the fight.
Aside from the mechanical benefit, it creates bonds that came up in campfire RP and discussions and led to in game connections and friendships.
I would note that the characters that are more self sufficient do not see the same level of connection and interweaving of stories.