With Project Panama, they are finally trying to make calling non-Java code easy.
Also because libraries in other languages often have platform specific dependencies.
That was indeed done on purpose, Mark Reinhold has had a talk about it once, but as noted on the sibling comment that is being fixed.
Re:Java Turns 25 – Whats Next? [pdf]
by imtringued on Monday September 21, 2020 @04:28AM
(#24541042)
It wouldn't be portable if it wasn't written in Java.
On the other hand, they need to have everything. In many other languages, it's common to just use a library written in a different language. For some reason, the foreign function interface of Java seems to have been designed to be hard to use, so instead of using an already existing library, Java developers tend to go through the route of "Rewrite It In Java".