As evidenced by several photos posted in this thread, when it's really snowing and blowing and freaking cold out hoods on top of helmets are awesome.
Kludges. Inelegant bodges.
Proving popularity of something doesn't make it the right thing to do. Shitting near the door of a filthy bathroom is popular.
No helmet has as much coverage as a hood. If it's really storming, my hood will be up.
Then that's a problem with helmet design and shouldn't be addressed with coat design.
There is no hood on the current market that has coverage that
a) moves with your head.
b) protects your face and goggles in the direction you're facing
c) allows helmet sizing to be independent of shoulder width sizing.
Every last "hood" on this page could be miles improved by cutting it off the coat, setting in a back-pack-style sheet spreader frame at the shoulder yoke and putting in helmet provisions, along with a proper precipitation-deflecting brim.
Of course, then it would be a "helmet cover" and not a hood. Which is the point.
The longer helmet covers are bound to "hood" thinking, the longer we're all going to be wearing chainmail in a world where both the visored sallet and Japanese auxiliary armour have already been invented.