I would say that those "starmaps" would be data tables compiled for a computer to access rather than to read visually. Visually, they'd be practically useless for precision course plotting. As data tables you could have a computer extrapolate the data into a visual for the humans who weren't doing any of this course plotting, but you wouldn't want your nav computer to use something that imprecise. Might as well do it yourself in that case. They even say that the star maps are basically sets of coordinates compiled as someone flies through and charts the system. Coordinates indicate tables of data, not drawings or "turn left when you see the kinda blue-white star over the yellow planetoid". I mean, consider the scale of the map they were looking at in the movie. There's a lot of space hazards you'd miss looking at that because they'd be too small to show up.Literally just read an article about this yesterday or the day before saying that these types of "maps" are used exactly as I'm saying in the Star Wars universe and that Star Wars Rebels explains it.
http://screenrant.com/star-wars-rebels-canon-season-2?view=all
read number 22.
It would also mean that pulling the map Rey saw from her head using the Force would get you a useless picture if you're Kylo Ren, even if it had been complete. The only way that would be helpful would be if Luke were on a planet already in a well-charted system, they just didn't know which one. Then they'd already know all those small details you wouldn't see on the map and they wouldn't be a problem. But then, why would you need a whole map instead of just the coordinates of the planet? And you end up realizing there's no point to the whole visual map thing.