Writing software is hard, especially for something as complex as the operating system on your phone. When you take millions of lines of generic code and try to wrangle it into something designed for a particular group of phones, a lot can go wrong. That's exactly what's going on when you see companies offer beta versions of the next big software update for your phone, just like what Google is doing with Android 15.
Google does the lion's share of the work with Android and has to make a solid base that works as intended (or close to it). At first, it seems never to work as intended. Case in point: Android 15's first public offering is so broken that the company has pulled the update image, forcing users who want to try it to manually install it.
