Comment by Aurornis

Any time you introduce an explicit incentive, however small, to open source work the unintended consequences can become a problem.

The Hacktoberfest incident is a good example: The program offered a T-shirt to people who had a PR accepted. The result was tens of thousands of useless PRs across open source repos and maintainers begging for the program to stop so they could stop dealing with useless PRs. https://joel.net/how-one-guy-ruined-hacktoberfest2020-drama

In a situation like this you can’t assume that the set of people and the type of work being submitted will remain the same as before the incentive appears.