And this is when they are not actual employees so there is at least legal cover. If Google made them employee it would be 100 times worse.
Mind you, I am not somehow advocating that Google must not hire them. From a culture/ country other than America, I see people can be treated with respect but not paid lot of money mainly because there is not much money to around. But people receiving also understand not a lot of money can be given for certain tasks.
However modern media culture is worst. If Google were to hire full time, I can see headlines "World Richest company pay pittance for back breaking work". And point about job security , benefits would be forgotten.
One can check coverage of full time Amazon warehouse workers on how it plays out. I have never heard a good story about it. Or how other companies hiring warehouse workers doing compare to Amazon across America or world.
I mean, this is the case at any company really. The highly valued people or people in the management structure are more highly valued and have more say. The very org structure alludes to a class system.