It was an offer. Take the snip and get 30 days off your sentence. The offender is not compelled to take the offer.
Personally, I think more than a few of them welcome the idea of avoiding potential future obligations for child support.
How ‘bout we do this for any/all WELFARE instead? If you can’t support yourself, should one be procreating??
Better idea would be to eliminate government welfare. At minimum, peg the benefits so that if you have another kid, your benefits do NOT go up. Ever. Eliminate any program that makes it viable to have kids you cannot support.
Incentives work WONDERFULLY!