Some profits (income above costs) is legitimately earned: the first mover in a viable market will certainly enjoy profits before his competitors develop.
But, for the most part, 'profits' are actually what Adam Smith termed 'Rents' - as in
Rent-Seeking, whereby government influence is used to generate income.
An example would be the income that accrues to the holder of a liquor license in a town that is loathe to approve liquor licenses. Note that not all of his income would be Rent - if he actively managed his establishment, some of his income would be wages for labor; if he owns the building and the stock, some of his income would be interest for use of capital.
Other examples would be the profit made by a Public Utility; the profit made by the holder of a FCC license; the profit made by the owner of a Taxi Medallion; the profit made by a polluting power plant (when other, newer plants must comply with stricter laws); the profit made by banks who can charge interest on money they don't have. In general, if you accrue wealth or income due to some piece of paper issued by the government, it's Rent. One way to tell is when a government license can be sold on the open market: how much do liquor license go for? How much to taxi medallions go for? How much does broadcast bandwidth go for?
While a corporate tax would theoretically catch all of these profits, the fact is that special interests have filled the tax codes with beneficial loopholes. What is income? Hard to define. While no system is proof against tampering, most Rents can be directly assessed; alternatively, many of these government licenses lend themselves readily to periodic auction.
Of course the lion's share of government created value is in Real Estate, in the form of land titles. And here is the crux, a whole lot of people are property speculators, and accrue wealth through the ownership of their own lot. Unfortunately, these people tend to rabidly defend their lots from taxation - much to the benefit of the tiny fraction of the country that owns the majority of land value.
Hopefully, since property taxes are generally the purview of states and localities, more jurisdictions will adopt such a form of taxation. Currently, several municipalities in Pennsylvania do this to a tiny extent, and have seen economic improvement. The Netherlands used to raise most of their public money this way.