I can only imagine that if Ford did offer Expedition with cabin filters, there'd be mad numbers of people complaining about the unethical added cost of routine maintenance. How they are nothing more than mold magnets due to their dark and often moist environments, about how they do nothing but restrict HVAC airflow, pure marketing gimmick accusations. Then there'd be complaints of clogged evaporator cores, how they contribute to a hard-to-clean film build-up on the windshield, how they hold onto smells rather than actually filter them. Surely some complains about how they should be stand alone options and not included in packages, gripes on dealers charging too much for the service while also creating their own false intervals, complaints of used dealers not changing them. You'd hear from those of us in the midwest who frequently drive on dirt and gravel roads. Always there is a guy (or gal) who has to point out how there have been cars for 100 years without these gadgets, etc. You know, the same things posted regularly on the BMW & Infiniti forums that I lurk.
K&N makes a washable cabin filter for a handful of vehicles and as you might expect, some people argue until they are blue in the face that those filters don't work either.
Maybe Expedition window regulators are designed with your health in mind? Keep those windows up people. Except you claustrophobics, go ahead and put yours down. Point is, Ford never has and never will be able to please everyone.