Many newer city transit busses in US 'kneel' when they stop. The air suspension lowers the front of the vehicle to get the door sil closer to the ground. Then the body raises again when the vehicle starts moving.
Most large city bus maintenance departments would hate wheel covers, and they would end up damaged or 'lost'.
The wheel covers could be important to protect the tires against UV
Folks with large motorhomes in the US frequently put canvas/vinyl covers over their wheels when parked. Since most large RVs don't travel but a few thousand miles per year, the tires can be ruined by UV
damage before the tread wears out.
I would expect airport tarmac shuttle busses to have relatively low mileage. They get used a lot, but the trips are short compared to a city or highway bus.
Those busses also don't appear to have the lighting and bumpers required for highway use in the US.
Yes they are neat looking.