It's not rare at all. Any field where the company or person paying for the code has absolutely no ability to do anything with it themselves anyway. And frankly

It's not rare at all. Any field where the company or person paying for the code has absolutely no ability to do anything with it themselves anyway. And frankly people tend to keep and reuse their code anyway, but I prefer to be honest about it. Here's an example I did: fast linear algebra algorithms in C to run an algorithm on a customer's device. They wanted the high level algo working, not my matrix code. I used it in other stuff for a really long time. One doesn't need everyone in the world to unanimously agree to one's license terms. It's fine if you're repulsed by the idea. That's a important flag when considering potential customers.