When you release something, your work is not done. You have to maintain it, fix bugs, release patches, and probably the worst part, keeping it up to date.

For example, Apple decides to deprecate some API, or decides to switch cpu architecture, or for the millionth time change how app signing works, or add some new security feature that breaks your app. Now you need to make your app work properly on the new platform, switch APIs, all the fun. Or, there's some critical vulnerability in library you used and customers are deleting your app from their computers (a lot of companies use automated scanners that check against published CVEs). It's most fun when you learn that the new version that fixes the vulnerability completely breaks compatibility with the old one and now you have to rewrite all the code that used that library.

Also, maintaining open source projects is not fun. It's a lot of work, in most cases unpaid, thankless, and building a community around a project is really hard.