Among other things, there are three primary reasons:
I don't have a house keeper so I'd love him to at least wait until he gets near a laundry basket so I don't have to go around the house looking for shorts that were cast aside by my little heathen and tossed in some random direction in the same mindless lord-of-the-flies ritual he preforms nearly daily but never in quite the same way.
It makes it really, really super hard when I had plans to go back out, to get him motivated when he must now put shorts back on.
Lastly, it's a little bit embarrassing when other people come over and he forgets and does it in front of them (like, right in front of them). I know I said younger but we're talking reading age so he's quickly approaching the point where non-family are going to view it as odd rather than cute and being a single dad, that kind of scrutiny is something I worry about.
Don't worry, though - more often than not, he still does it when it's just the two of us.