Casual Sex, Romances are boring.
Good for you! If you want casual sex without romance then Astarion is going to be a great companion for you. And Lae'zel. :]
I firmly believe that not including both "friends/strangers with benefits" and "love and romance" would be a error in a CRPG that is determined to include any sort of sexual interaction. Some people want sexual interaction for fun - no emotions needed, and some want romance - no sex necessarily needed. Both are fine, and including enough companions to cover both types instead of having all companions belonging to the same category should be easy enough. Sticking to just one personality is going to alienate the population that is looking for the other option, which means a more narrow audience = less money for the game developer.
Romances doesnt sound like Larian at all.
I take it you did not play DoS2.
In Witcher, you wanted to score.
Witcher is not Larian's creation, so not sure why you brought that up as an example. Besides, 95% of the book fans and a decent share of the games-only community would disagree. I find few things as entertaining as reading the "Yen vs. Triss - who is the best wifu?"-threads. There is at the very least as many people looking for romance as there are people being like "idc, I just want to see tits."