An air fryer is an appliance with electrical parts, including probably some fragile cheap electronics, moving parts (the fan that blows the air around) and parts made of different materials in a machine that is going to experience lots of cycles of heating and cooling. That is to say, there is a pretty sizable room for wear and tear. Hopefully it'll last you many years, but one doesn't really expect a machine like that to last for generations, especially considering things like planned obsolescence. A pan has no moving parts, no powered components, nothing but a hug sturdy slab of metal formed into a specific shape. As long as you take care of it properly to avoid corrosion, there's not really anything to break about such a thing. So the idea of the later lasting practically indefinitely makes sense, the former not so much.

Probably because normally you'd expect to outlive the air fryer but not the pan...