I recently saw this sign in an ice skating rink. Everyone in my group was wearing a helmet, and it proved to be a good thing as one person fell and hit her head. Apart from a headache, there was no lasting damage. Had she not been wearing a helmet things would have been much much worse.
As I walk around the streets of Oakland and see all of the Lime and Bird scooters flitting about, I have no doubt that we will start to hear about scooter related accidents with greater frequency very soon. This conclusion stems from the fact that scooter drivers predominantly operate the scooters on city sidewalks, and the scooters are capable of achieving speeds that are clearly unsafe for sidewalks. Collisions will occur as people step out of doorways and get clobbered by a passing scooter, deviate from a straight line when a scooter is approaching from behind or other scenarios.
Sadly, of the hundreds of riders I have seen since these programs started, I have yet to see a single rider wear a helmet. While you "probably won't need a helmet today," why not wear one anyway?