This is a bad assumption to make - that agricultural, industrial and asteroid stations will be dirty and untidy because not wealthy and not hi-tech.
The look of a station should not be related to the type of station, but to the state of the system the station is in.
Even a hard scrabble station in a processing system just getting started might be spotless, indicating good discipline, leadership, and pride.
If you've ever been to a leading hi-tech ag or industrial facility they are spotless, but one that's very old or not doing so well may be run down.
Even some old ones can be spotless, with just worn but well maintained machinery. Big difference in feel!
That is far more accurate than just dumping garbage on agricultural, industrial and asteroid stations because they do processing type work.
Rendering a bit of garbage on the floor to make it seem "untidy" also actually looks like a cheap effect that doesn't really work, especially when the general texturing still looks brand new. If a place is is untidy, it's generally run down all over (ie: word texturing/machinery etc) and the place looks well-used, not brand spanking new with a few papers, drink cans, and coffee cups on the floor.