It’s hard to argue against hiring contributors, but a bounty system that pays pennies vs. market value for skilled developers shouldn’t be the only interview path, it’s borderline exploitative.
Few people with no innate interest in the project are likely to ramp up and start contributing just for a shot at a job. Whereas if you’re Facebook or whoever you are much more likely to get people who don’t care about the product and just have decided they can make a lot of money by jumping through the right hoops.
Lots of reasons why you would want to simultaneously pay well and not attract people who are optimizing for pay.
You get a small reward in return if the contribution is accepted and you get to contribute to the world corpus of knowledge.
I'm shocked that interviewing still works how it does in large companies; the Sybil attacks and DDOS are just getting started.