This arrangement is mutually beneficial.
Individuals receive training at no cost and with no risk. They just pay the usual tax rate. They’re effectively paying for their own training with their future tax.
Governments pay nothing upfront. They can increase the skilled modern workforce, overcome skill gaps, and help those in need, without worsening the budget! Importantly, there are mathematical ways of structuring the contract, so they only pass on in the future what they otherwise would not have had.
Investors get low-risk, high yield, short-term returns. They can do well while doing good. A true win-win.