When you're getting paid per job (by a landlord) you don't waste time removing doors. There's no "pride in your work" either. The AC doesn't get turned on until next week. Sometimes the water doesn't either, so every extra minute there sucks.

You also just follow whatever the last guy did. If I'm first, I cut in fixtures. It's just as fast as covering them in paint.

You can also just put tape over the hinges and cut them out with a boxcutter and then paint. You can leave the cabinets up and still not paint the hinges. There's really no excuse.