Well, I don't know if it's a bad practice or not, but I never scrub anything, with the exception of my fermentors, and I only got an infection once, and that was my second batch of beer ever made. I think that had to do with not rinsing pink stuff out of the carboy enough....the beer had a chemical taste.
Carboys for instance...I rinse them out with hot water until they look clean, then put pink stuff in and shake it up...let sit 10-15 minutes, then rinse well.
I do similar with my kegs too...I've never touched them with rags or brushes...just rinse with hot water, then put in starsan, seal, hit with CO2, shake, and put on the shelf.
I wonder if I haven't run into issues because I don't let things sit before washing them? Or maybe I'm asking for it?