Are you referring to tax accountants and lawyers and such? If so, read up on "deadweight loss". Spending billions of dollars complying with income taxes is no more useful than spending billions of dollars paying people to dig holes and fill them again. It ultimately produces nothing and is a net loss even if some come out ahead.
Yeah, but these people went to school for a long time, and paid alot of money to do so too.
You eliminate their industry in one fell swoop, they have nowhere to go, really. I mean, you eliminate the tax code, what in God's name is a tax lawyer going to do, cause for the most part, he specialized in a certain kind of law.
Not to mention, accounting firms often use a great deal of their profits to invest in other kinds of business ventures, taking away that capital in one fell swoop would not be a good thing.