For German insurances, scooters are usually considered safer than motorcycles.
For an insurance there is no "should be" or "just sucks", only (historic) facts.
And they don't need to explain their data base (from statistical bureau) or draw conclusions for traffic safety (*), only the calculations made.
(*) Thats a matter i.e. for the "Institut für Zweiradsicherheit". Many publications online available. But I doubt, everyone would like to read their expertises.
<=125cc <=11kW <=80kph Kymco scooter for my (16 yr) daughter: 289.33€/year liability insurance.
<=125cc <=11kW <=80kph Kymco motorcycle for my (16 yr) daughter: 518.59€/year liability insurance.
You can calculate it yourself at huk24.de or any other online portal.
(And no, 80kph on a motorcycle is not faster than 80kph on a scooter.)
Perhaps we could agree on the possibility that motorcycles may be theoretically technical superior, but just their technical superiority overkill does the damage.
Well, in my country and many others, insurance does not depend on "subclass" of vehicle. 500 cc scoot is in the same insurance class as 500 cc motorcycle. (and, interestingly, 500 cc quad!!!)
I believe that it requires a deep knowledge of insurance and actuary mathematics to understand the way insurance amount is formed. It is not easy or straightforward.
It depends on statistics and probability of an accident and average damage paid out by the company, in a way that the company in the end does not lose money.
Most important factor is number of covered miles. Scooters are generally commuters and cover several times less miles than motorcycles, and at, generally, lower speed.
For sure, motorcycles generally are much more hazardous than scooters. However, statistics is not available that would compare equal displacement and power.
If one would analyze for example super scoots like 800-850 cc vs. 800-850 cc motorcycle, most likely some interesting results could be found. Or 500 vs 500.
Of course it is more difficult to get killed by own fault on 50 cc 4 stroke scoot that barely does 25 km/h uphill than on 1000 cc 200 hp sportsbike.