Currently The incentive to make local maps is pretty much the same incentive as to screenshot then all, and make a map with it....
After all, you can do far more with a Bunch of local maps put together in photoshop then you can with a region map ingame, there are several reasons for this and several changes needed for maps to have a purpose [other then to quickly port to a 3rd party program].
Map [already works 3rd party] Features:
{Necessary to render using 3rd party applications defunct}
-Adding Points of interest/labels to locations. [Insanely important]
-Titleing/signing of the map
-Making region maps that can contain 'unfinished' localmaps [You can do this in photoshop, and theres really no reason why you shouldn't be able to have some holes in your local maps, it would greatly increase the ease of making maps of purely waterways and the like]
-Make regions maps zoomable/higher resolution [They do lose information from local maps due to shrinkage].
-Combining region maps into even larger world-maps?
In addition to those, what is really needed to keep ingame maps important and valueable and worth all those hours that went into making them is some sort of ingame use.
-Would also be nice if you are in the maps area, if you showed up on it as a x or something...
-Have them interact with the travel system in some way: [Some ideas how this might work]
-Decrease travel exhaustion if locations you are traveling from/to are within map / increase if don't have map.
-Allow maps / signposts to interact to allow a user to fast-travel to signposts that are on the map
-Fast-travel to villages on maps
-Travel to anywhere on map
-Travel to Points of interest
Also, perhaps some restrictions could be added on such a feature, like not being able to fast-travel if the player is not in the map's bounds, or there needs to be a route [ie, filled up map] between the point you are traveling to and from.
The truth is the maps really need a use INGAME, to make them have value ingame.... otherwise people will just port them to photoshop right away..
Edit: also..really could use some sort of carryable map-container, like a mapbook..
a single region map is 25 local maps, keeping track of it all and organizing it for multiple region maps requires lots of chests... which seems excessive for a punch of paper.. really could use say a 26 page mapbook that can contain 1 region map and 25 local maps... possibly more?