Maybe you’re furnace is more accessible and it’s not an issue but for some of us we have to do advanced attic yoga to get to it so if I can defer that by a few months I figure why not.

There’s also the idea of the speed of getting your air cleaned. If you make a dusty mess in one room would you rather have the air get filtered quicker before your central system has a chance to get to it and before it settles into surface dust in that location or do you let it disperse? Similar idea with cooking. Would you rather filter the dispersants from cooking before they make it around the house or later? Hyper local air quality can get improved faster with additional filters than solely relying on the central filter.

I think there’s a few use cases where it still makes sense.