My husband would have been dead if he hadn't worn a helmet on his commute.
I'd suggest that most people who say "I'd/he'd have been dead if I/he hadn't worn a helmet" are almost certainly wrong. If he only had a minor concussion and needed no medical attention then it was almost certainly no worse than what I survived without a lid. The thing is people see the broken helmet and think what a bad impact that must have been when helmets are designed to break and will do so without a huge impact force.
that fact is it saved his life.
That's an assertion for which you have zero evidence.
"It is a surprisingly small number of folk who get squashed heads. A dozen or two not all of whom would be saved by helmets."
Has it occurred to you that this might be because helmet use is pretty prevalent among cyclists, particularly in branches of the sport which tend to feature regular falls and crashes?
Has it occurred to you that the stats haven't changed much and there wasn't an epidemic of cyclists dying due to head injuries before helmets were as universal as they are now (we're only looking back 10 or 15 years here - have several guidebooks featuring lots of pics of people riding MTBs without lids)?