Used to work on an application that mostly did string manipulation and we couldn't upgrade it from 8 to 9 (or 11). Java 9 got compact strings (8 bits instead of 16 per character) if you used only a subset of UTF-16 (the LATIN-1 charset apparently, which english is). We would have gotten a free speed and memory improvement but the ops refused to support it, even though we did everything ourselves ):
So even if there's a reason to change, people wont do it.