I did pest control work for several years, I saw some mind boggling messes. Mummified rats in kitchen drawers, stoves full of roaches, you name it. We used a special flushing spray, sometimes roaches would cover the entire floor after we used it. You could lift a picture away from the wall and the space it covered would be shoulder to shoulder in German roaches. The insides of tablecloths would be covered where they hung over the table.
And these were real homes inhabited by people who had all this filth??