The banjo was one of the instruments that defined the sound of early jazz.
Probably the best known player from that era was Johnny St Cyr, who featured prominently on recordings by Louis Armstrong and Jelly Roll Morton.
Banjoists continue to play a prominent role in revivalist ensembles recreating the sounds of 1920s New Orleans, but mainstream jazz quickly left the instrument behind. Many banjoists, St Cyr among them, doubled on guitar and, over time, most simply switched instruments. We think of Eddie Condon and Lonnie Johnson mostly as guitarists, although both were capable banjoists as well.
In group performances, the banjo has one major advantage over the acoustic guitar: it's a lot louder. With the advent of electric amplification, however, this ceased to be an issue and, as the guitar became associated not just with playing chords but with pioneering soloists such as Django Reinhardt and Charlie Christian, it acquired a certain glamour that made it more attractive.
I can think of no major modern jazz guitarist who today plays the banjo seriously as a second instrument, and only one serious modern jazz musician who chose it as his first: Bela Fleck.
There's more than jazz to the music of Bela Fleck and the Flecktones, of course. He calls it 'a mixture of acoustic and electronic music with a lot of roots in folk and bluegrass as well as funk and jazz'. There is, nevertheless, plenty of jazz in it, and in the music on a new CD, The Enchantment (Concord), which places him in an unlikely pairing with Chick Corea.
I say 'unlikely' not so much because of the styles of the musicians - both are known for eclecticism, and their common ground includes large personal collections of Grammies, Fleck having eight to Corea's 12. The improbability is that of the instrumental combination. Banjoists aren't often heard in duets with pianists.