Kick scooters' small wheels have set the inspiration for the battery powered scooters.
Small wheels make it easy to mount and dismount the scooter. They have little angular momentum, so speed up faster and slow down to a quick stop faster, which is ideal for urban busy traffic.
They turn direction and weave through the traffic or sometimes sidewalks easier.
But the trade off is, they hardly can take the road bumps or puddles. They are wobbly and unstable.
New designs are trying to remedy theses defects by using a larger wheel, suspension, setting the caster angle more leaned back to add stability.
In scooters design, fashion plays a big roll in among other things, sizing the wheels, mostly because of the young consumer in this industry.
In bicycles the engineering of efficiency, low drag, balance call for large, narrow size wheels up to a 29-inch diameter. The frame should be designed to be comfortable, give the rider flexibility of a more vertical gait for power pedaling, at the same time let them lean into the wind when cruising. They have wind tunnels and test drag in different configurations. Another advantage of a large wheel aside from control and a smooth ride is large angular momentum gives the wheel stability when rolling fast if they hit an obstacle.