In my family we also wash the sheets about once or twice a month but we're pretty picky about our hygiene otherwise so there's simply no need to do it more often. Shower every day at least once, different pants when we're inside the house and we don't wear shoes when inside either, that's just gross.
And we wash our cloths quite often.
Plus we have these things called chairs for our guests to sit on, so they don't get dirt on the beds.
