I think romance is included in a lot of stories because it is a very common component in life. We have so many experiences around love, and exploring that in a fictional environment at the same time we do battle against demons is fun for many people.
TTRPGs cater to you choosing your own story. To remove the romance from this story is to say that some choices in this story cannot be made.
Also, there’s mods to remove the romance. It would be a loss to have them gone at the onset.
You are making a silly argument that is flawed. The Witcher includes sexual themes because the book it is based on also includes these themes.
BG3 includes optional romantic themes because the game it is based on can include optional romantic themes. The game is about your involvement in the story, about how you navigate the world and its people because it attempts to mimic DnD. You can do a lot of “I seduce the dragon” and BG3 was designed to be fairly accomodating to a variety of tables.
To suggest the game would be better if it contained no romance when you haven’t played it is… bizarre? Especially with it being optional. But, that is perhaps the epitome of my argument. A lot of content in BG3 is optional. To remove any of it would be to make a game about options lesser.