Honest answer? Because there are literally no repercussions for the driver doing so. And they know it.

Seriously, what are you going to do? Report it? Yeah, right. And if you do, what do you think will actually happen as a result?

Best case scenario is that the person at the other end manages to keep a straight face while "taking your report." Yes sir, zjheyyy88, that's terrible! We'll get right on it. Thanks for bringing this to our attention.