I imagine the restaurants and their lobbyists will get their way, and a carveout will be passed. I also think that once the public finds out what happened, it will sour them on the restaurant industry. It's not like restaurants can't charge the same prices under the new generally-applicable law. The only difference is that they'd have to make the pricing transparent by including all mandatory surcharges in the price of the food itself. If every other business in CA will be required to do so, why should restaurants be exempt?
"Effective lobbying" seems like an unsatisfying answer.