What's old is new, what's new is old. While bunks have never really been "common" or widespread, they HAVE been available in at least a floorplan or 2 from most manufacturers for many years, both class C and class A. My brother's 1986 Tioga class C had bunks, as did my neice's +/-2010 Fleetwood class A.
And while overhead bunks (in a class A) are considered a relatively new option, that is not really the case either. Nearly all of the really early class A's had drop down bunks over the cab area; my grandfather's class A had one in the early 70's. They kinda fell out of favor by the 90's, but now seem to be making a comeback.
We don't stop playing because we grow old...We grow old because we stop playing!
2004 Itasca Sunrise M-30W
Carson enclosed ATV Trailer
-'85 ATC250R, '12 Husky TE310, '20 CanAm X3 X rs Turbo RR
Zieman Jetski Trailer
-'96 GTi, '96 Waveblaster II