I don't understand how this works - why would couriers want to work for something which has no provable value? I mean until (if ever) it has a stable and relia

I don't understand how this works - why would couriers want to work for something which has no provable value? I mean until (if ever) it has a stable and reliable value you would essentially be working for free. I guess you could use investor money to buy back the generated coins thus ensuring value at first but it doesn't seem like a sustainable business model.