I don't know where you are living Sciolistes but your comment would be fine if there was no penalty for making a mistake. Unfortunately most of the civilised world is covered in controlled/restricted airspace and the UK alone has several hundred serious busts a year, so "something" needs to be done and dead reckoning is clearly not going to get any better because that horse has been flogged since about 1910 and anybody who thinks that major progress is just around the corner a century later is kidding themselves.
And once outside the civilised world, one might just get shot.
Sure, DR works if you do it right, but there are so many ways to make a mistake, and there is plenty of terrain even in the UK where there are few features.