You get what you pay for.

Every one of us spends our lives building on our experience and then presenting that experience to others in exchange for compensation.

Without a system to manage this, it's just something to be exploited.

How do you as the employee know that someone isn't going to have you do a bunch of work and deny you compensation, or request you do more additional work than what was agreed upon?

How do you as the employer know that someone isn't going to just take your money and not provide the requested work or provide something substandard?

If you can't build a reputation on either side, there's no reason for anyone to trust you.