The opening paragraphs of Brian Priestley's sleeve note to Jazz Combo from "I Want to Live!" (Affinity 1988) are worth reading in this context:
"The influence of nostalgia runs through much of what passes for jazz appreciation. Doubtless it always has been a factor in cases where the individual fan is out of sympathy with more recent jazz but finds that the jazz of his youth has a continuing impact. The effect of this on a musician's career is sometimes beneficial in terms of employability (in fact, musicians only ever feel nostalgia themselves for earlier successes when the employability barometer has turned down irreversibly.) It's often less beneficial, however, in encouraging continued creativity although (to be fair) creativity has sometimes fallen victm to other pressures even before they become the object of nostalgia.
The musical developmemt of Gerry Mulligan and his constantly renewed vigour, long after his original period of celebrity, proves that loss of creativity doesn't always go hand in hand with popularity. This fortunate fact emphasises that the undeniable nostalgia rating of his 1950s music - again, like a lot of nostalgia - depends as least as much on image as on sound. So, of course, people remember the tunes (and probably the solos too, since those records were so very well-known) but also they remember the crew-cut cover-photo of Mulligan's famous 10-inch LPs. And they no doubt recall that, on his first visit to the UK in 1957, he looked like an animated version of that iconic illustration. Unusually, as far as image is concerned, Mulligan had a second bite of the cherry, for the flowing-haired full-bearded sage who toured with Dave Brubeck a decade later has gone into the collective unconscious as well."