I always wear a helmet while riding. To me its just a cultural thing, most of those leather neck wannabe sons of anarchy types like to ride helmetless.
Dudes that ride harleys and stuff.
Generally those bikes are slow anyway, and most of them are only weekend warriors, only ride around town and to the local bar. leave the bike parked in the garage half the year. so i think for them they think the possibility of a crash is low so, they don't care about safety. dudes in the pic above pretty much confirm this.
People who aren't part of that harley club, typical daily commuter types generally like to wear helmets. Not just because of the safety aspect, You can also hook them up with bluetooth and listen to music gps, communicate with other riders ext. just provides more modern convenience. we not trying to adhere to the 50s greaser stereotypes.
Depending on your social group you either this type
or this type
