If the lady in the rat way knows your a vampire and after stage 4 if you have DG every else knows your a vampire how come they don't attack. That was the entire point of feeding. What are they thinking, "Ehhh if I say anything vampire rights groups will come I will be stuck in a lawsuit forever, I will be labeled a bigot. Its best if I just leave it be".
That is gameplay reason right there. Remember stage 4 had regular attacks, but since the kids and the babies kept tearing up complaining about being attacked, Bethesda removed it. I hate the fact that we don't get attacked no more and the feeding and blood potions is useless now. Thanks Bethesda, thanks a freaking lot.
Anyways, it is gameplay reasons. Truly, vampires would be shot on sight for being what they are. It is basically a crime against nature to be a vampire, according to the creatures known as mortals who are at the bottom of the food chain compared to vampires and werewolves.