I don't get this. People install their program, contribute the power of their computers for free and Gridspot takes money. Why would anyone do this? Why would

I don't get this. People install their program, contribute the power of their computers for free and Gridspot takes money. Why would anyone do this? Why would anyone contribute their computer resource for other people to make money from that? I would rather, I don't know, mine bitcoins or set up a Tor proxy.