Certainly not, but requiring any purchase decision be backed up by someone wanting the thing helps quite a bit. That's something that naturally follows in the private sector when we give people cash, and frequently happens in the public sector when things are working right, but is undermined by pressure to build out projects to "provide jobs" - and a guarantee makes that worse.
I'll note again that I'm certainly well in favor of improving our infrastructure.
I don't either, but there is no silver bullet to avoid boondoggles. Moving everything to the private sector certainly doesn't prevent them.