Why not lower the bottom rate from 10% to 5% and send the other rates back to Clinton levels?

Lower income earners would receive a tax cut. Other income earners would receive the same cut that would be gradually eliminated as income increased and was taxed by the higher Clinton rates.

Yes, I know this sort of progressive tax change is pie-in-the-sky; but why don't we have progressive Democrats advocating for changes like this one to the tax code?