Are you letting stuff in your backlog that you'll never get to before the product is gone or irrelevant "slide"?

Sure they could round those people up pretty easily just by following up on any contact with the system that they have, but why, for what, to cost the state more money that will likely never be repaid? Especially when sticking a body on DUI detail is hugely in the black. They'll just let that debt, it's accruing interests and the threat of further incarceration linger on the books indefinitely. If the person ever gets their life together they'll have to pay it or face incarceration.

I'm sure someone somewhere has written a DB query to select from outstanding balance where <exists in some other DB that is a proxy for people who have money to pay> and prioritize those cases.

Your family isn't sleeping under a bridge or whatever. Of course the system wants your money or the money of people on comparable economic footing you associate with. If you can work as a debt slave to the system it wants you to do that even if it means a never ending cycle of robbing peter to pay paul, sleeping on other people's couches, etc. The man sleeping under a bridge cannot, so the cops and the DA and everyone else just go fry bigger fish. Maybe they push the issue 1/100th of the time and incarcerate someone every now and they but they absolutely do not prioritize it the way they do someone who could pay even if only by moving heaven and earth. The system doesn't want to manufacture yet another felony and then incarcerate someone for it out of thin air, that just costs the system more money.

Source: my tiny keyhole view into the system. The parties involve always have have discretion to downgrade stuff to something else, or not pursue it at all and are incentivizes.