It's all about supply and demand, my friend. If everyone on that platform was upset with the wages they were making they would refuse to work / find a different avenue that paid them more. But it seems like there are enough people on those platforms that are happy with what they earn to make it a successful business.
The more open your network is the lower the prices of the work will be (upwork, 99designs, etc)
The more exclusive your network is, the higher the wages will be (Crew, Toptal)
It's all about supply and demand, my friend. If everyone on that platform was upset with the wages they were making they would refuse to work / find a different avenue that paid them more. But it seems like there are enough people on those platforms that are happy with what they earn to make it a successful business.
The more open your network is the lower the prices of the work will be (upwork, 99designs, etc)
The more exclusive your network is, the higher the wages will be (Crew, Toptal)