[DragonSubie7]

If you drive in a clean, especially non-dusty environment, your filters will stay a lot cleaner, for a lot longer.
If you have a used filter in the car, and you can't tell it apart from the new one, chances are it doesn't need to be replaced.

A tech at a dealership might not change it either.
Do you really need to wash a clean car? In either case, if you did or didn't, how could you tell?

Driving on dusty dirt roads like I do, means a filter change is usually needed when the oil needs to be changed.
Fortunately, both are easy on a Subie, and cheap to do as a DIY.

The service intervals would be incredibly complicated if they had to describe every possible environmental condition, but they attempt to provide a general caveat to the normal interval if you look in the manual. More often in severe conditions.

Since you need to change filters more often in severe dirty conditions, it would seem to make sense that a change isn't needed as often in much better (cleaner) operational conditions.
I doubt air filters on equipment near the North Pole ever need changing.