I guess to put AI vendors on an equal footing with human intelligence vendors (ie humans). Workers are taxed on their revenue - their gross earnings - not their profits.

If the point is to tax AI consumers then AI providers can collect that tax on behalf of the IRS.

Taxing the profit of AI companies is useless since profit is a number that is easily manipulated to 0. Taxing revenue is much more direct. Prices have to go up to cover the tax. Hence the consumer oays "more" and that more is passed onto the tax man.

Taxing profit is exactly why businesses pay so little tax - it's trivial to make "no profit". (For example if the IP is held in another jurisdiction with a lower tax rate, and is "licensed" by the company which wants to make no profit. )