Shouldn’t these kind of sites also include a productivity indicator next to each individual salary? Considering how much individual productivity varies for IT w

Shouldn’t these kind of sites also include a productivity indicator next to each individual salary? Considering how much individual productivity varies for IT workers knowing just the salary is like knowing the price of a bag of, say, flour in a supermarket, without knowing the volume. Also, to push the analogy forward, how about the flour quality? One employee could be more valuable for the business due to stuff like his willingness to help in tough, boring but critical moments. Or learning more outside of work to be able to apply that knowledge in new and innovative ways inside the company. And so on... Are all those factors sufficiently captured by a single number like "level"?!