It's a long-standing issue/debate at this point. The maintainers of long-term stable kernels have for some years now used scripts to automatically pick as many appropriate-looking stand-alone patches as possible, looking at what's merged into Linus' "tip" tree (usually to find fixes targeting rc(N) kernels). Since they do the work they get to decide, but many others have found this an inappropriately regression-prone way to manage longterm-stable kernels. If you want all the latest fixes and improvements, you can use the latest kernel. If you use the longterm-stable it's because you want less risk from unrelated/unmotivated changes, you want only the specific fixes found to be most needed.

Well, that's all in my interpretation :) for more broad background see https://lwn.net/Articles/863505/