> You're only seeing the dirt accumulate suddenly and visually in the snow.

doesn't dirt accumulating in the snow make it extra dirty? just like when it rains, the dirt is washed away so it's cleaner

how is it a visual bias?

normally when i walk my dog and wipe their feet, black stuff comes off. after it rains and i wipe my dog's feet, it's pretty clean.

similarly with snow, my shoes and pants get splattered in spots from the dirty snow's dried mud.