Taxing revenues means that outsourcing any aspect of a business automatically incurs an e.g. 5-15% fee over doing it in-house. That would artificially incentivi

Taxing revenues means that outsourcing any aspect of a business automatically incurs an e.g. 5-15% fee over doing it in-house. That would artificially incentivize vertical monopolization, removing some of the natural benefits of specialization, and could destroy low-margin businesses altogether. Europe's value-added tax approach seems like a better alternative, though I'm sure it too has drawbacks.