It’s the default because Java has a history, and it was set when everyone was deploying war files to machines with 512mb total memory and the default worked for 95% of people for the past 25 years. In fact, it’s still good enough for the chocolate factory that has brainwashed you into drinking the static binary milkshake.
Of course there are ways to use all the available ram when you deploy your kubernetes pods, you just have to consult the documentation.
Honestly this criticism is ridiculous I can’t believe I even bothered to reply.
Imagine launching every app and having to say ok you get 300mb but not more!