Because the audience isn't "programmers".
https://link.springer.com/chapter/10.1007/978-3-030-79876-5_...
Microsoft also sponsored David Thrane Christiansen’s book, Functional Programming in Lean[1] (which I’m sure you know about!). That is another indication that they intend to reach programmers.
[1] https://leanprover.github.io/functional_programming_in_lean/
Are people like these not programmers? https://leandojo.org/