Right, except that we don't have bundling of all dependencies of an application. Welcome to Linux, enjoy your horribly uncomfortable stay unless you have a large team of people who know what API/ABI stability are, and can also claim to keep bug compatibility. (I've yet to meet those people, unfortunately) The impact of this is that if you just upgrade one part of things, you massively bloat out the number of combinations you have to test. And if any of those have a problem, and you miss it, well done - you just broke an application for an end user.