Originally Posted by otc
I'll still do it if asked...but if the best reason you can give is that "its dirty" I am just going to assume you are a bit of a germaphobe
If you sat on the curb and happen to sit in dog poo/mud/motor oil/pool of water, pretty sure you will be changing out your pants VERY soon.
If you happen to step in the above, chances are you will probably scrape your feet on a clean patch of concrete or wipe it with some towels till you feel it is dry/clean, then continue on.
Hard to compare the two I would say.
But to be honest, if you showed up a someone's door with jeans/pants whose back side is blackened with mud/whatever, would you think it is odd if the host asked you to take off your pants and leave it outside?
Some people are perfectly ok with scraping their feet on the welcome mat and step into the house after such encounter. The same people probably are not willing to sit down on someone's carpet if their pants suffered the same treatment and they only wiped it a few times with a abrasive surface.