...and they're missing out, that's exactly the message. By the way, I'd be shocked if Java 8 was still more than half of the running server-side JVMs. There's a lot of them for sure, but I'd be willing to bet it's gonna be less than a half now, and declining.

They continue to use Java 8 as they see to reason to change. Article like this are meant to motivate those laggards.

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.