Indeed, I also have had some problems in the past with 'hackathons' I attended which were heavily organized around competition prizes. There were obviously teams simply goal chasing for prizes. Which I felt the organizers pushed so hard for that it went against the 'spirit' of hackathons.
There's plenty of personal gain to be found being an OSS developer (especially in a group setting just outletting creatively with other talented people) without directly making the motivation prizes/money the end goal.
No one is against rewarding OSS developers as much as possible. I'm certainly not and think every successful company using OSS software, aka all of them, should have a wing donating to projects. But I am against watering it all down to some narrative of OSS developers somehow being exploited by commercial companies.