> if you care about your own
Given how few of the riders are wearing helmets, they seem to at the very least be unaware of the risks they are taking.
> ... and others safety.
Power is intoxicating. Being in a more powerful vehicle on a surface shared with other less powerful vehicles makes some people ignore others' safety, or discount the way in which their actions imperil others.
Anyone who has ridden a bike/motorcycle in regular traffic can attest to that experience around cars: you assume you are invisible to them. I've seen many high-powered cars/trucks/motorcycles swerving and accelerating dangerously around less powerful vehicles in traffic.
Similarly, I've seen motorcycles driving fast down bike lanes to get around car traffic.
It's a similar situation between the scooters and pedestrians on busy sidewalks.