Sales tax (which most US states collect) specifically is a tax on revenue, but it is the exception.

When taxes are paid on revenue rather than profits, the rate is obviously much lower, so that it would add up to roughly the same thing.

However, there are many benefits overall. For one, it completely kills off the various convoluted schemes to avoid classifying something that is obviously a profit as such (by shuffling things around subsidiaries etc, for example). See also: Hollywood accounting.