They say the reasons are many but basically that many of the issues in the older version have been fixed with their software current versions, and they don't want to have to fix them in every issue. They also say that it is easier for employee management to just keep them trained on the current version or those that are not EOL yet, it cuts expenses and overtime.
It also keeps their archive repository at a lower volume which saves space on their drives which saves money. And also that many of the associated libraries that go along with the software are updated and it is very hard to find those older library files or alternative replacements, so it just makes sense to keep people current.
And all of this does not even cover all of the deprecated functions and other coding that is no longer supported by PHP/MySqli as well as Apache. So folks the developers are not trying to make your day miserable by asking you to update. They are trying to keep you in the stream of better performing and more current functions and features, which will allow your server and software to run better, faster, and safer.
Software has the same rules as life - its about change and how you cope with it because change is a constant static value in our world. You can choose not to change but then you get left behind. The choice is yours :)