Allow companies to pay felons less for the same job, at least for some finite period of time, to compensate for that risk. Otherwise, as you say, it makes sense for them to hire people without a criminal record, other things being equal.

The truth of the matter is that us felons do work for less – at least I did – mostly because we have no choice. We are also less likely to be promoted. Three times I had job offers withdrawn because of my criminal past. Having much more to lose than someone without a criminal record I never considered doing anything illegal, or anything that would cast a shadow of doubt to my integrity. “Once a criminal always a criminal” is just not true. Unfortunately, too many people subscribe to the false cliché.

Most of the software companies I've worked for don't care about the relative salary cost because the all in cost and opportunity cost of a bad hire is way higher than the salary. For example, given the choice between a proven senior dev making 200k or a risky untrained dev making 70k they'd still just hire the senior dev. It's more about headcount with the big companies. They don't care about saving 40-60k in practice, from what I've seen.