I dont really know how to word this actually, but here are some thoughts.
In RPGs, development is the measure of progress.
Being forced to explore the map, even if the developer is moving you from point A to B in a linear fashion is still better than nothing at all, obviously
Simple world mechanics like having to build a bridge before crossing it only in later game to fly and entirely ignore that bridge is one classic example of the point I'm trying to make.
My point. Certain physical obstacles that are overcome add to the development of the characters, not in stats or plot (usually) but the player will now recall the time when he had to walk from Ding Dong Dell to Castaway Cove before fast traveling, he rekindles the wonderment of exploration just by revisiting a place and reconnects with the world as a whole.
It is a side-effect of the world map. It enhances the immersive ability to view the world as a whole. As one cohesive entity.
I love world maps in JRPGs, but I don't feel like it's required or even count it as a penalty if they don't have one.
One recent example would be Xenoblade - with the way that game is structured and the setting, a world map really wouldn't work all that well imo. So the way they did it - huge areas to explore - with no world map was perfect.