Taxing revenue instead of income would be an extreme incentive towards vertically integrated businesses, making all other choices uncompetitive.

For example, if a chocolate bar is sold by overseas manufacturer A to an importer B then to a wholesaler distributor C then to a small retail shop D then to you - then if taxes were paid on revenue, then that chocolate bar would be taxed 4 times, and each step would bump the price up by the tax rate in addition to the current markup; However, if a manufacturer A would buy all the elements in the chain and sell it directly to you, then it would pay 4 times less taxes, and it would be impossible for others to compete with that pricing difference.