Except when the AI businesses have lots of available money, so they might not care about the extra taxes (they're spending billions anyway). There's also the problem that they might destroy the future agricultural worth of the land with e.g. polluted waste water.
Given that they don't want agricultural land used for data centers, it makes more sense to just ban them rather than allowing it if they get some extra cash.
Please let's not fool ourselves that AI businesses don't care about costs because they have a lot of money. They burn a lot of money, yes, but they are looking for profitability and they won't achieve it with a 200% tax on top of large energy bills and hardware expenses.