Because adding the word "diverse" to the text of to their output is a lot easier than retraining their model? They're always going to try for the easy fix first.

Have you never tried tweaking the error text first before giving up and redesigning your form that's confusing users?

Hmmh. Fair enough. I didn't think about it from the perspective of "error text", but now that I think in that mental model, I think you're right here.