Helmets are such a funny thing. Like many things we do it's all about perceived risk vs. real risk, ones' own personal limits for risk, and even about public perception and peer pressure.
For example, I, personally, would NEVER ride a motorcycle on the street without a full face helmet. NEVER. And I have proven to be religious about this, as I used to do the motorcycle work commute thing. And I don't have to, because I live where there are no helmet laws (thank goodness!) But I don't bother to put one on if I take a small dirtbike for a leisurely buzz up one of my trails in the woods. And I despise helmets for bicycling. I will freely admit to this bizarre behavior. From a safety standpoint I should wear an appropriate helmet for all of those activities. But I don't because I feel the risk/reward ratio tilts in the favor of no helmet
for me except when on a street bike. The reward is, admittedly, likely to be considered a poor trade-off by many: a feeling of freedom, more physical comfort, better visibility, etc. And yet it tilts back the other way when riding a motorcycle on the street. I can't give you a purely logical argument for how and why I draw the line on helmets, only that I do, even being very well acquainted with the risks for all of these activities, as I was an EMT on a municipal ambulance service for eight years and saw all manner of non-helmet related injuries.
There is also public perception and peer pressure at play. Riding a sportbike and wearing a helmet is considered completely normal in the US. Riding a Harley and wearing a full face helmet not so much. Stupid? You bet. But people like to fit in. Luckily I'm a sportbike kind of guy!
Looking at helicopters, particularly small helicopters like the R44, I would certainly find the the use of a helmet uncomfortable. That alone stops me right there. I have made a risk/reward decision and it came down on the side of "no helmet". Maybe that's stupid, but it's my choice (until some nanny-state yahoo creates legislation--please, please don't do that!) And there would be potential perception issues that would cause some colleagues to find it pretentious and some passengers to worry, but those are lesser and less valid factors. But some people put a high value on "fitting in".
Finally we come to the money issue. Anyone coming up through the US civilian helicopter training world is well familiar with budding pilots who live hand to mouth, eat only Ramen noodles, wear ripped and dirty clothes, because nearly all of their money is being spent on helicopter instruction. These are the folks borrowing school headsets. They legitimately are not going to pony up for a $2500 helmet. Every dime goes to pay for helicopter and instructor time. This applies to many newly-minted CFIs, too.
So, since I can't fly a turbine, don't have a helmet and aren't wearing Nomex, I guess I should just stay in bed? OK, being a little snarky there. You can even get killed in bed
But, seriously, while it is perfectly reasonable to point out that we would all be safer with helmets, please recognize that it is not something that everyone wants to do, and please don't MAKE us do it if we don't want to unless we work for you and you demand it. That's fine, your playground, your rules. But otherwise...
All I can say is that my risk/reward line is drawn where I choose to draw it, even knowing and understanding all of the risks, and understanding that wearing a helmet is much safer (and I can afford one, a GOOD one, for every activity, too). It's a complex, personal decision that is not fully driven by logic.