Lack of imagination. First, the biggest complaint sould be that it's regressive. Second, no one would accept 1-2% tax on retirement assets, even though this would actually benefit them over a long haul: grow tax free for 40 years, and then pay a n% asset tax, where n=asset pool (your retirement account) age?

Almost everyone does better with Roth versions of IRAs and 401(k)'s anyway. Pay the tax up front, no tax at the back end, and thus basis and record keeping isn't even relevant.

There's a bunch of ways to simplify this while also making it fair if it weren't for the greedy rich people who want regressive taxes, i.e. flat tax.