Or you have a heavy, inbalanced object in your car you don't want sliding, something fragile in tow you don't want to have fast decelaration, or just don't have super-human reaction time since some light have extremely fast yellows.

Or, a deer jumped out on the side and you briefly looked away at it.

Or you could tell the driver behind you wasn't slowing down, so the safer option is to go.

Or. Or. Or. Real life is messy, and there's a million reasons to go though a yellow instead of slowing down.