Time. For a solo / indie shop, you have limited time. Every time macOS/Xcode/iOS updates, some of the iOS APIs are deprecated in favor of "the new better way

Time. For a solo / indie shop, you have limited time. Every time macOS/Xcode/iOS updates, some of the iOS APIs are deprecated in favor of "the new better way of doing things". You have to keep up, or else your old apps stop compiling at some point.