I don't think jazz electric bass guitar is anything really new
A fair amount of bass guitar used in mainstream jazz:
Lionel Hampton switched to using bass guitar in the early 1950s.
Monk Montgomery switched to playing bass guitar in the 1950s.
Buddy Rich switched to using bass guitar in the 1960s.
Steve Swallow switched to playing bass guitar in the late 1960s (he claims seeing Cream was the reason)
Sonny Rollins switched to using bass guitar in the late 1970s.
Is it because BGs are easier to transport, and/or amplify? Is a BG actually preferred for sonic/tonal reasons?
Yes and yes. I've been on bills where the other band's bassist was using a bass guitar because either he couldn't bring his upright or it had been damaged during the tour
