Honestly I don't care what motivates people to contribute to open source. Some people are previlaged enough to contribute for fun in their free time. Some do it for improving their resume (Not everyone is previlaged to work in a FAANG or reputed tech company or went to an Ivy League). Some do it for improving the software they use. None of the reason is honestly better than the other. At the end of the day what matter is the code gets commited to the repo. Nobody mentions the reason why they made the contribution in commit message. Don't worry about maintainers getting overwhelmed by contributors. Its a good problem tp have. Most of them are smart enough to come up with a system if that problem actually arises. Honestly the main reason most open source projects die is not because of too many contributions. Its because of lack of contributors and a single maintainer having to do all the heavy lifting by themselves.