Globally they can’t, there is a tiny program in some parts of California designed presumably for local regulars, where some drivers can influence rates. https://www.msn.com/en-us/money/companies/uber-lets-some-cal...

Of note the way it’s implemented is actively designed not to be used. Effectively Uber lets those drivers multiply their existing calculation by some number but not for example simply set a minimum charge or actually negotiate individual trips. Further, regularly declining trips is not accepted.