those people probably set that bugger and then don't worry about it from then on out.
i do get irked a bit by the people in the "fast" lane who go whatever speed they go, even if it's above the limit, and won't get out of the way when a faster vehicle (me) comes up behind them. they figure they're going 70 or whatever and that's fine with them, so up yours, you can deal with it! ARGH!