Threatening to withdraw would send a clear enough message that most idiot lawmakers would back off because it'd make them unpopular with their citizens (who want their iPhones to work), and they only care about maintaining popularity so that they can accept bribes from corporations to pass legislation.And they didn't actually do it
More so, most people didn't pay Google for anything.
If you disrupt millions of users by shutting down your app store and blocking them from making use of their $1200 device that runs their daily lives, they are going to hold it against you. If you end up blocking their work apps that have a subscription because you no longer want to process fees to make a statement, they are going to leave for a different platform.
What is your end goal, to voluntarily and permanently deeply erode Apple's Market share in half the world because you are butt hurt that the governments want some regulations on Apple's App Store?
Apple isn't being a child here, it's these lawmakers. Apple would send their customers a notice saying that due to their government trying to corrupt Apple's products, they must withdraw from the country by X date and that users can contact their local government to try to prevent the new laws forcing Apple to accept alternate payment methods / sideload / add a USB-C port / etc. The backlash from these users against their malfunctioning government would sort it out quickly and Apple wouldn't have to withdraw. If South Korea or whoever really wants to call their bluff and force the issue, how many days without working iPhones until the backlash from users was great enough for the government to reverse course? Not long, I'm willing to bet. The alternative is Apple bows to every ridiculous government rule and we get a trash product like Android