I mean, more kisses would not be rejected by the part of the playerbase that stayed around for the romance. It wouldn't really make sense to give the same amount of variety to everyone, though -- Gale is a fairly stable person, for example. He doesn't need 2, 3 or even 5 sets.
Gale if funnily enough a pretty good example for when different sets of kisses make sense. Throughout the game he has his normal kisses which are all very sweet and lovely, but once you enter endgame with him, he has a new set of endgame kisses. They are all of them devastatingly desperate and highly emotional and they are absolutely perfect because they serve the purpose to show you how scared he is of loosing the final battle. (Which might get important later on, depending on your choices.) The kisses change, because his state of mind and the situation the two of you are in changes.
