Scooter’s undermotorized?

Hello, I would like to add a maxi scooter for me for the next year, but if I look at the “PS” number in the 250-400 segment, it is not so impressive to say honestly. My favorite is a Yamaha X-Max 250 which has only 20 P.S. But. If I compare now for example with Kawasaki Ninja 250er which already has 33 P.S. the difference is just crass. How do you think why the scooter engines are so much undermotorized compared to motorcycles? The Yamaha X-M Ax 250 has certainly been doing nothing new for 15 years now and apart from an injection system. No desire to invest in new technology? Or how can you understand that?