I think box fans are used because that's what people already have around. When wildfires rendered our air here in the PNW unbreathable last September a lot of f

I think box fans are used because that's what people already have around. When wildfires rendered our air here in the PNW unbreathable last September a lot of folks were scrambling for something that would work quickly. Waiting around for an SUV cabin fan to arrive and then trying to figure out an enclosure made that a non-starter.