The same thing happens with street performers in general, the good ones never have to ask for attention because the show pulls people in on its own. I've seen it at farmers markets too, the vendors who just sit there quietly with great stuff outsell the ones yelling deals all day. Begging for attention makes people think you don't have anything worth their time, but showing off the real thing does the work for you.

The real move is muting by sound, not by length, because the dancing lizard jingle is the actual thing that drills into your skull, not the 30 seconds it takes to play. You could also do a keyword mute on brand names and let the short stuff through if it's not the same three companies hammering you every break. Half the reason those dumb ads stick is repetition anyway, so cutting the repeat offenders does more for your sanity than a blanket time limit.