The scooter brand that seems to be most popular, the one starting with M. It's a Swiss brand/company. The founder initially developed a product for adults. He was wondering how to improve getting around, when it is just a little bit too far to walk (for lazy sods like myself), but not far enough to make it worth getting out your bike. So he developed a scooter for adults. It was hugely successful.
For a few years, in places like Zurich, the streets were populated with businessmen, bankers, CEOs etc in suits scooting to/from work, scooting to get a sandwich for lunch, scooting to meetings. It has tapered off now.
The kiddie scooters are just a lucrative spin-off.
So, YABU. Scooters are MEANT for adults.
In our family we have a scooter each. We go to the park on a Sunday, and rather than having whining kiddies complaining 'I don't want to go for a walk!', we go for a scoot instead and all enjoy it. Also beats watching the kids have fun - we join in instead; and is much better than running around after them!