Fedora opens up to bundling

that's effectively what people are doing, except that there are other people who are modifying and enhancing a portion of your codebase. some of those updates you take. others you don't (at least not right away)

Remember that in some cases, the people writing the code are only releasing source, they aren't creating or shipping a shared library.

Expecting an app developer to first turn a pile of code into a shared library, then finding someone to maintain it for the distro (including said bugs and security holes), before they can use it for their app is NOT less work.