Front licenses are the law in California, but TEN percent do NOT put them on. Officers can ticket, but usually don't unless there's some other infraction. Then it's a twenty dollar fine, usually. I put a license on the front of a car for the first time with the 3, but before that I only got a ticket once in my life. Not sure I needed to do it. So I understand why a dealer wouldn't put one on. If you wanted it on, you should have asked for the service, and I would guess they should have billed you extra, which I would guess you would have expected for free.
Hey, it's only a couple screws! Sure you're busy, but I bet you sit and watch football or some other waste of time. None of us are so busy we can't screw a couple screws into a bumper -- it takes literally 5 minutes.