You're talking about the wrong level of abstraction.

Think about the problem as this: A worker sets up a website offering services. A potential customer is looking for a local purveyor of that service to hire. How does the customer find the website? If there are 25 local workers willing to do the job, how does the customer choose between them? If the customer wants to pay with a credit card, how does the worker get the money?

That's the role that Uber et al are playing. It's possible to decentralize that but it's not trivial.