The driver doesn't have the ability to turn up a dial and say "I'm going to charge more now".
(This isn't the only distinction between an employee and contractor though of course)
A licenced taxi driver cannot do that, either.
If instead, my analogy were that I was a general contractor who built water slides and a water park put out a bid on construction of a water slide and refused to negotiate, my only option is to take that bid or leave it. Why does it matter what the water park is going to charge the people to ride the slide?