I think the main engineering reason why cars have cabin air filters is to protect the heater core and evaporator from plugging with dust, and not for air quality, despite what the marketing department may say.
Next you're going to say something trollish like that the air filters in furnaces is only to protect equipment. Who cares. What I *need* it for is air quality and I'm the one buying and paying for it, so give me what I want.
-If you won't turn it on then nothing else matters.