> One of the biggest criticisms of Java is that it consumes so much memory, for which the rebuttal is the JVM can be tuned to use less! But no one does this in practice, so I assume there must be a reason that renders the “tuning” argument to be penny wise and pound foolish

Nope, the main reason is simply that memory is cheap and plentiful, so there is simply no reason to spend any effort to tune base memory usage when writing the kind of applications Java is typically used for.