Not because of JIT, but because of refcounting GC. Also the JVM probably loads (and does, or at least is prepared to do - http://www.azulsystems.com/blog/wp-content/uploads/2011/03/2... ) too much crap. (And probably the jigsaw and modular and whatever OpenJDK projects will help with that.)
Furthermore, Python is not really memory prudent either. PHP is much better in that regard (very fast startup time, fast page render times, but a rather different approach).