don't forget that the failure rate for these new helmets with larger vents is greater.

Helmets still have to pass the same certification test with less foam, so the foam had to be altered. Helmets that pass the tests are harder and break more readily than the older designs that had more foam that broke apart less often.

Then again, to most people a helmet breaking often reassures them that the helmet saved their life, so maybe a helmet that is less protective may be also be more often perceived as providing more protection. A replacement purchase racks up another sale for the company too and perhaps even raises more sales as those who's helmet has broken tell the tale of how the helmet saved them, even if all it did was fail by breaking and not compressing (which is how these things are supposed to work).