I've encountered oncoming riders with a lot of different lighting setups, and I've yet to figure out what the supposed benefit is to high intensity helmet mounted lighting for road riders. For that matter, I also don't understand some people's desire for 800+ lumens of light for an on-road (or MUP) commute, either.

I fully understand it for off-road: You need to be able to spotlight rocks and tree branches and dropoffs, all the little things that could seriously mess up your ride if you didn't know they were coming up. The Lupine Betty or E3-Triple make sense for 24 hour O-R events. A strong helmet light makes sense.
I just spent 5 hours riding in the dark on Saturday night, on unfamiliar roads with descents in excess of 30mph. I've got a single Supernova E3 symmetrical light mounted low on my front rack, and it was plenty of light. On my helmet I have a Princeton Tec Quad LED which I switched on when I needed to read my cue sheet. If traffic is bad during my commute, I will sometimes turn the Quad onto flasher-mode to get noticed.

Honest question to everyone: Aside from the ability to jacklight a driver like a mule deer, what's the benefit to having a 600 lumen helmet mounted lighting system for a road commute, especially one with a symmetrical lens (basically anything helmet mounted sold in the USA)?