Why would we be interested in this? What does it have to do with Raspberries?
Perhaps not much now a days. But bear with me:
The Raspi uses an ARM processor. That ARM processor has a linage going back to the first Acorn RISC Machine built by Acorn in the 1980's. Which, interstingly, was the fastest personal computer one could hope to buy at the time.
That Acorn RISC Machine was inspired by the concepts of the "Reduced Instruction Set Computer", RISC, as championed by David Patterson at Berkely https://en.wikipedia.org/wiki/Berkeley_RISC
Those RISC researches lead to devices like Spark, MIPS and Alpha as well.
So, anyone inspired to learn about programming and computer design by exposure to the Pi might also be interested in the history of such things. The MIPS is part of that history.
Should any young person here be inspired by the Pi to undertake an undergraduate degree in computer architecture they are quite likly to find themselves studying the MIPS architecture as an example.
Does anyone give a flying?
For us guys that have been living through and following the development of micro-processors for the past four decades it is of interest. It's the end of a famous line.
Given the Raspi Foundations goal of furthering knowledge of computing I would say that MIPS is an interesting part of all that.
Mind you. You are right. It's all history now. MIPs in it's pedagogical role will in computer architecture will soon me displaced by the RISC V.