I can completely understand why some folk prefer larger party sizes, but I don’t think it’s anywhere near as simple as single-player vs co-op.
From your side as a player, sure, it may not seem that way. But from the side of the developer, it is absolutely things like co-op v. SP. Their game building decisions cannot factor in gamer opinions about anything since they won't have solid data in that regard. So their decisions are going to be made based entirely on their vision for the game. And Larian's vision for BG3 has been, from the very beginning, that it should be an awesome couch co-op/Stadia game first, and SP only as a secondary consideration.
