> Has this always been an issue in academia, or is this an increasing or new phenomenon?

The introduction of this article [1] gives an insight on the metric used in the Middle Ages. Essentially, to keep his position in a university, a researcher could win public debates by solving problems nobody else could solve. This led researchers to keep their work secret. Some researchers even got angry about having their work published, even with proper credit.

[1]: https://www.jstor.org/stable/27956338