Not so simple. Many taxpaying Americans keep zero savings. They spend what they earn. Their inability to forecast tax liability and the April 15th payment would bankrupt them. Also, I don't find the estimated tax system simple or easy. https://twitter.com/rationalwalk/status/951824487477075970 …
I think that, even if it didn't bankrupt them, the people would revolt. I've heard that similar changes to the way union dues are paid have also decreased union membership.