It's not that they don't understand; it's that it causes more work for the lawyers, because someone has to review the license if it's not one of the standard boilerplate acceptable licenses.

I once had to go to lawyers to get a license approved on a lib that went something along the lines of "this work is in the public domain; do whatever the fuck you want with it, just don't come crawling to me for help". I'm paraphrasing from ~20-year-old memories here, but I do distinctly remember the profanity. It elicited a chuckle from the lawyer and something along the lines of "I wish all of these were this simple".