I guess I'm ignorant but why do we continue overspending worldwide?

Like do these groups all have heavy metrics about how budget is growing so we actually know anything is in balance here?

I guess I've never seen proper studies around:

"We project tax revenue will grow X amount with this level of confidence therefore we know we can consistently be within Y range of debt growth forever safely"

Or are we all just hoping we all die before someone has to comes in and cuts services spending in half?