Comment by zadikian

Do you mean backwards compatibility for things that rely on the default settings? The defaults have already changed across Java versions and also depend on the system.

Normally when you run a non-Java binary, it uses very little memory to start, doesn't have a limit, and returns memory to the system when it frees things. Supposedly you can set JVM flags to do all that, but performance probably suffers, otherwise they would've just done that. So in practice users are always setting the flags carefully.