Google are avoiding an à la carte offering here. They are saying you either get search which now includes AI, or you can disable the entire feature. The obvious thing that people want is the original search without AI included.

They are not giving reasons why they can't unbundle these options. It could be technical but seems more likely that they want to appear to comply and shift the focus. Search being disabled creates pressure on those operating the tool. The local narrative becomes that the admin is the one that is limiting use. Eventually people lose sight of the real reasons and Google are on the sidelines watching users fight it out with admins.

This is a classic product management approach to dealing with objections. Remember that the PMs are getting measured on usage. If no one uses their feature then they are in trouble, so they make it hard to disable their features. A wonderful incentive structure, right?

Lots of companies build toggles that bundle up features as a result. You may want to disable this one thing, but toggling that off disables all these other things you want. The admin has pressure from the business or users. The vendor comes in to support the business or users, and then the IT team is overruled. Alternatively, the bundle is packed with items of real value plus mitigations are released elsewhere in the product (think: eDiscovery/logging/compliance) that cause IT to enable the whole bundle.