Governments have as much incentive as anyone else to save money. I shouldn't even need to type this but raising taxes is unpopular and tends to cause people to get voted out of office.
People need to stop repeating thise weird talking points about "the government" and its incentives. It's a big, complixated entity made up of literally millions of people all of whom have different motivations and incentives and non-government employees affect those not just in the super obvious way by voting but by every interaction we have with anyone who works there.
This is missing the point. If you got rid of taxes altogether it would reveal what really is being propped up tax money as opposed to actually being valuable enough to exist on its own.
>complixated entity made up of literally millions of people all of whom have different motivations and incentives
Which is why it's important to get the big incentives correct. Otherwise one of these actors will waste resources since expecting people to do the right thing without incentives does not scale.