I'm thinking it's to do with the second and third definitions for draw:
2.
to bring, take, or pull out, as from a receptacle or source
3.
to bring toward oneself or itself, as by inherent force or influence; attract
By that reasoning, the second definition would reference drawing a bath (you're taking water from its source to fill the tub) and the third would be for drawing curtains (you're pulling the curtains towards each other).
-hides-
That does make sense, hm... I wonder how many more of my insanities you can make sense of? *flicks through the list*