Back in the days before I fully understood FF programs and before I had found FlyerTalk, I heard this as the way to get upgraded. Has anyone ever been upgraded because they are dressed smartly?

I know I've been upgraded when I've been dressed smartly but the upgrade was because I was top tier on that airline's FF program and my class of travel was oversold. I've also been upgraded from Biz to First on a long haul flight when dressed casually (thank you Cathay Pacific! ) so I know that a suit is not a pre-requisite.

After flying SYD > LAX > LHR > HEL in economy in a suit years ago, I gave up on this as a method of getting upgrades. I have wondered though if there is any truth to it or if it's just another urban myth.