The "no deductions" idea sounds great until you try to apply it. Consider two people. One of them works for an employer and receives $X/year. Apply a flat tax to his income. The other is a private consultant whose work brings in $X/year. Applying a flat tax to his income isn't the same as for the employee. The consultant has expenses (computer, telephone, office supplies, travel to clients, etc.) that are necessary for him to generate income. The employee has no such expenses. Surely the consultant should be allowed to deduct those expenses from his income. The same applies to any small business owner. The expenses incurred in generating his income should be deductible before applying the flat tax.
The retail sales tax avoids these problems. You buy something, you pay the sales tax, regardless of whether it's a computer for your kids to do their schoolwork on, or a computer for your business.
The retailer doesn't need any deductions either, since he's paying the tax on his gross rather than on his profit, which involves deducting expenses from gross.
Simpler to administer, and avoids tax returns for most of the people.
I'm inclined to agree, but with the latest outrages, the IRS should be abolished.