There are 4 metin stones on the Snakefield, and the map has many objects, mountains and other unreachable areas, thus metins are spawned in the same place. While Desert Yongbi is a huge map, with 20 spawns of metin stones, so it was possible to spawn them in many locations.
I think its good as it is, to think about it snakefield is over farmed cause of the static spawns but desert its kinda less crowded cause alot of people dont want to run around and search for metins.
So you can either have the static easy snakefield but being over crowded or go at desert and search around and probably find more.
If desert spawns becoem static too then people will make a coupel of scrolls for there too and it will be over farmed too