Just this week in Vantaa, Finland three 12-year-old girls piled onto one of those electric scooters you subscribe to with an app and proceeded to get run over by a car at a crossing, killing one of them
The app is supposed to have an age restriction but it's easy to bypass and you're not supposed to have more than one person riding on one, which people routinely ignore
I hate seeing kids and teens speeding around dangerously on those fucking things and then just leaving them laying around on high-traffic bike routes because they don't give a shit since they treat the scooters as completely disposable
Fucking awful bazinga-brained Silicon Valley-ass idea and business model. Actually, there are also bikes you can use with an app but curiously you don't see kids doing reckless shit with those, almost as if electric scooters were uniquely terrible 
Helmet laws; 200 years of largely safety-focused design refinements; significant safety regulations regarding things like brakes, lights, where they can be ridden...
None of these things apply to scooters, which is why the injury rate for scooters per distance travelled is roughly 115/million trips vs 15/million trips for bicycles.
Scooters come with brake lights, indicators... And as far as I know, in most countries the scooters and bicycles are in a similar or same category so the same helmet laws apply to both of them.
The problem is enforcement and education - bikes are usually owned, not rented, and people have been told for years why it's important to wear a helmet. A bicycle is a large thing that you leave locked, and you can lock the helmet together with the bike. With scooters you'd have to take the helmet with you so it's perceived as inconvenient, and we don't have years of messaging saying "wear a helmet with your scooter".
But to me enforcement is a big part of this. I live in a cycling city (mind you, a cycling city in the UK is still significantly more car-centric than central/northern Europe), and I have never heard of anyone getting fined for not wearing a helmet (neither on a scooter or bicycle). I routinely see people wearing dark clothes and no lights in their bike. If that's in the regulations, then clearly the police have better things to do. If nobody gets a fine, and there's no education drilling into people's heads that the helmet is important, then people won't bother.