The quickest route to ridicule, it seems, is for aging rockers to proceed as if nothing has changed. The truth is, years have passed, and to deny this is a form of visual dishonesty. With his shirt thrown open during a rousing rendition of “Baba O’Riley” Mr. Daltrey — a specimen for his age, to be sure — unfortunately invited comparisons to his groupie-magnet self from the “Tommy” era. In doing so, he violated an obvious dictum for seniors: keep your clothes on in public.

But he is not the only offender. At 65, Iggy Pop still takes the stage wearing no shirt, just jeans, as if it’s 1972. It’s not that his body is not freakishly impressive for a man his age. Aside from a few sags and bulging veins, his torso generally looks as lithe as a Joffrey dancer’s.

The problem is not the image itself, so much as the image suggested, as if these aging sex symbols are still attracting hordes of groupies to the cozy confines of their tour buses.

That may well be true, of course, but when these flesh-baring rockers are men of Viagra-taking age, that’s a visual most people could do without. It’s like hearing that your grandparents still have sex: bully for them, but spare us the details.