"Why should the pilot wear a helmet, if there isn't one for me?"
We spend much time and energy persuading pax that helicopters are a pretty safe way to travel A to B and it would be impossible, practically, to offer charter customers helmets. An ill-fitting bonedome won't help much. Probably a more productive route in the charter business is to minimise accidents through good practice, decent engineering and sensible decision-making.
In the aerial filming world we do offer multi-fit helmets to the director if there's any low-level work to be done and the crews generally all wear them anyway.