I (obviously) agree wholeheartedly. It is worth pointing out that sometimes historical software is used for instruction, like Unix v6, but that doesn't seem to be common.

A gating factor here is that much of the time, old software doesn't run, isn't available in source form, the old hardware is long gone and there aren't emulators, etc. We also probably over-glorify some things from the past. :)

Making the Texas Persistent Store build again is a bit of a chore as it is C++ from 1994 and things have changed a good bit. But even things that last had a release in the last decade don't build any longer (like framerd). Much less something like SHRDLU which was written in MacLisp and ran on ITS!