Consider how the market for law enforcement might differ if prosecution was contractual rather than salaried.

Large numbers of prosecutions are carried out by contracted lawyers in many countries.

I said 'differ', not 'wouldn't exist'.

Yes, I agree, it is 'different'. You phrased it as a hypothetical, and I am telling you that many examples exist.

The OP is specifically about the USA, and that's the context in which my suggestion was offered.

Many countries allow private prosecution of criminal offenses (though this is infrequently used in most of those countries for a number of reasons). If you eliminate public prosecutors/district attorneys, people could privately prosecute pro-se or with the assistance of private counsel.

That's just one example of many biases inherent to the current system, and I wouldn't focus on it too much.

so people rich enough could prosecute just about anyone they want, and people who are poor could likely never get any justice if they are a victim - and you think that is an improvement over the current system?

In such systems, the person bringing the charges must pay damages if the charges don't stick. Remember, the bar for criminal conviction is much higher than in civil court, and anyone can bring a civil case in our current legal system.

One major flaw in our current system is that only the government decides who gets convicted and as the old adage goes, if the king controls criminal punishment, the kings friends get away with murder. Think about the current national conversation on excessive police brutality.

The Romans had already tried this.. not a great idea.

Well Vitalant gives me enough loyalty points for a t-shirt once a year, but I give blood because I think it's a civic duty.

I'm guessing people think this is snark. but I do generally mean it. If something is worth condemning some one to prison for it's worth lawyering it for free.

That no one can imagine some one prosecuting a thief pro bono should be a clue