@Charlie Clark: "The helmet is a red herring."
I fear it may be, and then the mandatory wearing of helmets could make matters worse.
I snowboard, and when I started, nobody wore helmets. Now the vast majority do, but we've not seen a significant decrease in injury, not even just head injuries. It's thought that the added feeling of security makes people more brave and take on slopes and tricks they might otherwise not, so the protection is cancelled by extra risk.
If this were the case with eScooters, being amongst traffic would place other road users in danger also.
Plus as eScooters are all about the convenience of short term rental, does a 'one size fits all' helmet add extra security, or are we going to get accidents as oversize helmets slip and obscure vision, or hands are taken off handlebars to correct etc?