Why is Jack in the Box locked when it's not closed yet?

So, I had the urge to go out to Jack in the Box just a few minutes ago. Yeah, it was after 11:00pm, but they were still open, and it was just a quick walk across the street, so I figured what the hell. I got over there and the doors were locked. There were customers inside the restaurant (damn it, I always misspell that) eating, and people standing at the counter ordering. But the doors were locked. The sign for the operating hours on the doors said it was supposed to be open until midnight. But the doors were locked.

So I just said fuck 'em, and came back home. Yeah, I suppose I could have stood out there in the rain and banged on the door until they unlocked it and let me in or something, I guess, but it wasn't worth it. Fuck 'em.