It isn't that simple. Yes, the key step is simply to recompile with a 64-bit slice, which takes about two seconds. But TidBITS News is an iOS 6 app; it runs under iOS 10 only in a kind of emulation mode, where iOS 10 pretends to _be_ iOS 6. If you open the project with the latest Xcode in order to recompile it and make it 64-bit, you are linking it against the iOS 10 SDK and both the code and the interface need to be completely updated. In effect, the whole app must be rewritten from scratch. With TidBITS News, that's not really very difficult, but you can surely understand why, for many apps, their developers would find this daunting. And if the app is free or does not sell significantly, what's their motivation?