It’s a trade off between realistic look and gameplay requirements.
If you build a very realistic map with its large distances and looking very natural e.g. in world machine, then you have the problem that the distances are just too big and the environment pretty boring due to matter that in nature you have e.g. big empty plaines see the exmple of the mountain area above.
For a good gameplay on the other hand you dont want to have to wander over large, boring areas, you instead prefer to discover, and come over interesting environments like clearings, caves, ponds, rock-formations, swamps…and so on… quicker, which means they have to be closer together than in real nature.
Think of the difference like wandering 5 km thru the grand canyon vs. wandering 5 km on new zealand from sea-level thru jungle up to a mountain.