I don't think it's people being rude or uncaring. It's jsut habit. I don't close my door "quietly" at home, at work, or at the supermarket; nor do i speak in a whisper.
I try to remember to act differently when I am parked next to a vehicle that has tissue paper thin walls and open windows, but Im not 100%. And when I hear a sound that is not harmonious with silence, I let it go. If you worry about these things I can't even imagine that you are enjoyin the experinece of camping. Maybe think about getting a differt hobby......:h