I grew up with that kind of summer rain in Illinois, too. After about five minutes of it, yes, a lot of (sane) drivers pull over. But it comes on very suddenly, and for the first two or three minutes, traffic flows continue.

If you're in the center lane and traffic is heavy on both sides of you, while your windshield (or camera) is overwhelmed with water, you need to keep moving with traffic for a bit -- or you get rear-ended.