I remember a 'Survey of Programming Languages' class in college. Perhaps a archeology of code class and things already done. You are right, I wonder how much of Computer Science knowledge is locked away never to be seen. Perhaps a tax credit for companies that donate their old source code to the Library of Congress.
Yes. This is one thing that irks me about these fads in programming, they all solve problems that have long ago been solved and then re-introduce all the bugs that were already discovered, fixed and forgotten about ages ago. Old software is a very nice repository of information about edge cases and real world complexity.
A $0.75 accounting error turned out to be named "Markus Hess". Precision matters. If it works good. If it works but you don't know why it works: bad. If it works, but has a small problem and you don't know why: bad. If you run a $1M budget and you're off by $0.75: bad. And so on. You really don't want to store anything to do with money in floats.