The point for me at least is that if you are flying with an up to date chart and have drawn lines on it and worked out your expected headings, then the GPS, assuming you can get it into a CDI mode of some sort by getting it to fly to a waypoint, will give you a very accurate way of flying your planned route. I don't generally have any airspace data, roads, towns etc displayed as they just clutter up the screen. If the line on my map shows it will clear controlled airspace then I fly along that line on the GPS, or slightly to the opposite side of it to the airspace then I am clear of controlled airspace! It doesn't matter a jot whether the aviation database is up to date or accurate! The airports and VOR's that you use as waypoints are unlikely to have moved!
So.... using a GPS, except where you are flying a familiar route in VMC with some sort of obvious ground features like coastlines or roads that you can recognise, you still surely have to draw lines on a map and work out your expected headings. Once you get in the air the GPS is a far more accurate way of making sure you are flying along the lines you drew than dead reckoning.
If you just launch with the GPS and its map as the only thing you look at you are probably going to get lost from time to time.