First of all it provides a visual cue as to the rate at which a podcast is being played at, a constant cue rather than an indicator that has to be found and read. For that reason, on a purely practical level it is useful.

More importantly though you seem to be suggesting that an interface should never make reference to the technologies that preceded it, for fear that a teenager might be made aware of something they've never seen before?

What a terrible thought, that someone might be encouraged to investigate analog audio technology. Why can't an interface be a history lesson too?