Because app developers have to jump through a lot of hoops to get into the app store, and even if every single app was pulled then the developers would have to jump through all those hoops again. And this time, Apple won't make it easy. Meanwhile, they are hemorrhaging money for every minute their app is not on the app store. On the other hand, Apple would give incentives to new applicants to replace everything that was pulled, and the app store returns to relatively normal within 24 hours since there are tons of apps out there that just aren't popular enough to be on the app store at the moment. Would you want to be the first developer to pull their app?