Do you mean to write "they all do not wear helmets"? or does "road cycling" mean something other than just using a bicycle on the road?

I see few if any helmets

https://www.youtube.com/watch?v=HbsMKxNORgQ

https://www.youtube.com/watch?v=ZfDVmUD_2eI

https://www.youtube.com/watch?v=lJypp7igJho

No, I mean they all wear helmets. Cycling as in road cycling, group rides, as a sport, not for transportation. They're not professional cyclists, they all have other jobs.

https://youtu.be/_QUPWs07mKU

I think they use those for aerodynamics also. But yeah they turn up in spring and summer. Not much outside those seasons.

I find them very annoying, they tend to be very inconsiderate. Cycling on the road where bike lanes are available, and when they are on the bike lane they tend to be agressive to normal cyclists if they don't move along as fast as they want.

They're not all like that but many of them are, which leaves a bad taste as soon as you spot these groups of wannabe lance armstrongs :P

I don't think helmets are worn for aerodynamics. IIRC professional race cyclists only started wearing helmets after in 2003 when they became mandatory. If there had been any advantage in aerodynamics the athletes would have voluntarily picked up helmets before.

Also, anecdotally, I am occasionally road cycling for sports and do wear a helmet at all times. However, I am certainly not doing that because of aerodynamics.

Edit for clarity.

And cycle commuting is part of the culture which probably makes it safer as well. Would wearing helmets make it even safer? Possibly. But one can always argue for incremental safety gear and processes.

Making helmets mandatory would probably discourage cycling. That happened in Australia at some point, and nobody wants that to happen here.

That said, some cyclists here seem to be downright suicidal. Helmet or not, if you run a red light against traffic while watching your phone, you don't seem to be very attached to living. I've even seen parents direct their kids into ridiculously dangerous situations. Fortunately car drivers pay attention even to stupid cyclists here.