The option to "fix" the evil romanceable NPC is much more common and send the wrong message I think (you are manipulating people just so they love you).
Um, well, call me old fashioned but I dislike evil so I like to see characters change their evil ways even if it is in a small way, not like a massive conversion overnight.
Also, when I role play a PC they never go into a relationship/friendship expecting to change the companion. It just happens, or it doesn't and ends in heartbreak. I can't say that any game has actually given me the impression that the PC is actively trying to change anyone. They give advice/opinions based on how you role play them, but even the companions do that.