I think the idea behind it is that in a steady rain, your wipers adjust their speed with how fast your car "runs into" the raindrops, so you don't have to fiddle constantly with speed settings.
I thought it was odd at first, but my winter-beater (a 1996 Ford Aspire) has two speeds of wiper: Low and High (no intermittent) so I'm used to hitting the wipers manually when the rain isn't hard enough to require full-time wiper action.
Rain-X will let you do 75 MPH and never need wipers if the raindrops are large enough. They just roll right off. I used to use this stuff all the time during the summer. DON'T spill it on your paint.
The GTO is sitting during the winter, I fire it up and drive around the block at least once every ten days (no garage). I avoid wet spots on the road so the salt residue doesn't get sprayed on the car. Can't wait for winter to be over.