Comment by exidy
Inherited from the 80s? Microsoft effectively inherited drive letters via an 8086 semi-clone of CP/M called QDOS[0], it was the basis for PC-DOS and later MS-DOS. CP/M dates back to 1974.
But Gary Kildall didn't come up with the idea of drive letters in CP/M all on his own, he was likely influenced by TOPS-10[1] and CP/CMS[2], both from the late 60s.
[0] https://en.wikipedia.org/wiki/86-DOS