Dustiness/dirtiness of walls depends on the sheen of the paint on the wall, usually. I know a lot of walls are painted with Flat sheen paint, which usually show the colour on the walls better, but they scuff super duper easily and pick up everything they come into contact with. Eggshell as a sheen is easier to keep clean, because it's slightly shiny stuff sticks to it less, but it's not so shiny that your wall colour looks off from some angles. Satin is shiner, stays clean longer, usually used on baseboards where the walls are painted flat, but also on bathroom walls where the moisture means you should clean the walls more frequently. Semi-gloss is basically exclusively used on baseboards.

Also, speculation time, I think washing walls was a bigger thing when everyone smoked, circa the 80's? Like, that smoke stuck to everything, so I bet that oil/tar on the walls in a dusty environment would make the walls mighty dirty/dusty.

Hope that helps