You won't get Jan Jansen, Keldorn, Jolee Bindo, HK-47, Kreia, Sagani, Durance, Grieving Mother and more, if you decide to make each companion romancable. And that's shame, as those are highlights (at least to me) of their respectieve titles.
This is actually a really good point and one I hadn't considered. I can't see Larian subscribing to such a thought process though...these forums are full of people who want to f**k Halsin and God knows who else. Sex really does seem a driving force in BG3.