People aren’t going to just pay taxes for public goods. However, if the investment had a return, such as with funding the government through actual public quoting of the “full faith and credit” of the government might be one proposal. If faith were lost in the government’s ability to government, the value of the stock would drop. That, in turn, would drive people to invest in the government again but only if the government had the credibility to reduce such corruption. And, in general, the government would avoid corruption because, otherwise, their stock would fall through the floor.