I wouldn't mind such restrictions because obviously people have diffirent tastes
But because we have only a few LIs as a rule, race restriction is just ineffective
Actually, race gating could be an effective way to expand the number of LI's on the implementation end.
The Devs have mentioned a few times that one of the harder parts of love scenes isn't dialogue or direction, but modeling. Even culmination scene needs to work with all available character builds, regardless of their build or height. One of the issues that made Dwarves a difficult romance subject was the extreme height disparity.
If you do race gating, you're cutting out the difficulty of modeling for all models and builds by, well, not. This cuts the number of iterations needed to model the scenes for the romances, which can allow you to use those iterations for something else... like modeling the romance scene of someone else who otherwise wouldn't get one.
If the limiting factor is modeling characters, race gating would be an effective way to cut costs to enable more romances.