Im sure they researched this and found most people didn't care and this is why we have a FPS, not a real RPG.
There are several characters that I really wish were romancable, but overall I'm pretty satisfied with the number of companions in the game.
I'm not a big fan of faction companions. Danse's involvement in the BOS questline causes me all kinds of inconvenience. I mean, sure, if you love the themed playthrough and want a companion to match your faction, then they are great. If, like me, you just want a favorite companion to follow you no matter what you do then faction affiliations can be a problem.