The reason I started contributing to open source was to learn new skills. It was a great way to work on real world projects and gain experience.
The project I was working on was community driven to a large extent. We had users and contributors from around the world and being one of the core maintainers, I basically had no quitting time. I was working around the clock and did not have any boundaries. I had a lot of work in the project. I was writing code, reviewing PRs, hosting community meetings, discussing project roadmaps etc.
After some time, I started working on open source full-time. I was paid by a company to work on their open source project. We had a bigger team and it made my life a lot easier. I had well defined jobs and I did not have to worry about other aspects of the project like I did before.