Here's my opinion. I too wish this was for-pay, and I signed up with that expectation. Helping people is effective and enjoyable, but only if someone values the help enough to pay for it. I'd be happy to even guarantee the work and not be paid unless they were happy with the result.

What always happens with free sites is most of the highest-value people won't offer their services, so it gets focused around less experienced people, which is more efficiently solved by non-live sites like SO.