Well so what, then they'll drive without a license. As long as the punishment isn't sufficient to make the person care enough you will only nudge the threshold a bit under which people actually feel it.

Edit: Same with using the phone while driving. It's one of the biggest contributing factors to road accidents, yet here the fine for doing it is barely above the price for a decent headset. So most just don't care and trust the fact that well under 1% will ever be caught because the police either doesn't care either or just doesn't have the manpower to effectively enforce it.