By your house most likely means the one in laurel heights which I've wondered about why it was the only one for years. I think I have it figured out. First, low crime area, see 24 hours Walgreens for a rough estimation of where that is in SF. 2nd near UCSF (all nighter college students). 3rd near California Pacfic Hospital, Doctors and Parents giving birth want coffee at all hours. Making it economically viable.

You guessed right. The grocery stores in the center, bryans and Cal-mart, close early though, at 7-8pm.