I guess the short way of putting it is that a good monitor simply logs all the factors an adept "manual" user would and makes the right calculations. Like anYthing else, if you don' allow it to work correctly (such as bringing the batteries to full charge every now and then), it's the old saw of "garbage in, garbage out".
We lived full time, for months at a time, on moorings, with journeys in between the length of the east coast that mostly involved anchoring or mooring. The Hatteras, as we inherited from POs, was a relatively AC intensive, energy inefficient and hungry boat. So managing the inverter batteries was a critical function for us. Like most things, if something is really important to you, you pay more attention to detail and learn a little more about it. Apparent from the responses here, that is not the case with most posters, so the casual or marina-centric boater can certainly dial things back a bit, focus-wise.