Hiring a plumber on a per job basis isn't the same thing at all and getting bids for jobs like this, works.
Do you seriously think that people should bid to fill positions at companies?
"Hey there Plumber, if you do this job, I'll give you health insurance for the two days it takes you to do this job. I'll provide a gym membership, free coffee, and pay your taxes"
In the case of plumber, the benefits for plumber to take the job is they get to make money.
Your analogy might work for short term contractors but not for a full time employment, where essentially you are putting yourself at your employers service virtually 24/7 with almost no extra pay while doing intangible (aka knowledge) work where the employer might get 5x or 200x return out of your work, but essentially you will just get almost linear pay raises (even including performance bonuses).
You cannot compare a full time knowledge worker with a gig worker that does tangible physical work.
Kind of like a plumber saying "We don't need to dig up your front yard and charge 9 grand, for 500 bucks we can robotically patch the pipe from the inside".
That's probably the best strategy. It removes the problem the plumber has when quoting a price, which is "how much can I soak this guy for?"
The "problem" at many companies is "we need someone to be able to continually identify and respond to a range of problems as they come up over the next 1-4 years".
There are loads of jobs that post exactly how much they're willing to pay, it's just that they're the ones which consider workers with the minimum level of experience to be a cheap, undifferentiated commodity they won't in any circumstances pay more than the fixed rate, and the rates tend to be in the $12 per hour range