It's a DnD game. It's also a RPG, and romance is a part of RP:ing and the romance subplots are dialogue options and can make you more invested in your companions. Look at how invested people became in the Mass Effect crew members and quite frankly the romances weren't even very well written in those games.
We also don't know the full extent and how they're going to work out in this game right now. But in DA:O for example the romances changed the story a lot and totally changed how the relation between you and your companions played out in the story. I dunno what it is with DnD fans trying to gatekeep DnD either, who are you to decide what is and isn't the right reason? When I played the game first as my Drow Rogue I was drawn in by the Shadowheart romance subplot, it felt natural to me I didn't do it to '' watch a cutscence ''. Same with Lae'Zel on another playthrough because I was RP:ing my character differently.
Saying that it's unnecessary is quite arbitrary too. That same logic could be applied to so much, ultimately very little content is absolutely '' necessary '' it's just a bad way of looking at content.
