The vampir bat shared the blood by mouth to mouth.

But the vampires didn't need to, because they were independent enough to have human's blood all by themselves. But as the time passed, when vampire population decreased, vampire had to go back to their old habit, old tradition to take care the young vampire's supplies who forbidden to go out and hunting.

And here is Hoseok, the young vampire. Who is curious why human kiss but they don't share anything, but just devouring one and other mouth.