Yeah I can see that, although in that case you do need to prove to your agent what you were making before, and if they feel it's not worth their time they will be more likely to pass on working with you.

But that's a whole paradigm shift in thinking about agency, and they're perfectly happy with how things operate currently. They would have to spend a lot more time actually negotiating.

In the case of real estate, the idea that you absolutely need to work with an agent is so entrenched that it's very difficult to get anyone to consider the alternative outlook.