playersexual should be the default because the people taking the default option probably don't have anything to say about anything and the relationships are side-content to some main quest in a game that is about strategy and/or dexterity challenges. mass effect was broadly not elevated by having set orientations. New vegas was but they wrote better and had something to say about the BoS.
if you're doing something purposeful with with the relationships then you should make actual decisions about them, and can do powerful things with your narrative about whatever experiences you're depicting. I don't think anyone anywhere seriously says you shouldn't.
saint's row 4 has by far the best in-game relationships in a game that isn't a dating sim or primarily focused on those relationships.