Diversity is very plentiful once you have many biomes, plants, and animals. But from a city and farming stand point, there is very little reason to pick and stay in a particular area. You can move all crops around easily, and contentiously farming the land has no benefit. Plants from any biome can be moved to another. Biomes are nothing but easily deformed terrain.
In a system with many soils types, as well as a nutrient based system within them, it encourages settlement of specific areas for farming and city building. Which encourages trade and general war far in mutliplayer, as land now has a much higher value. The longer a city stays in an area, the better the soil becomes, the more likely they'll stay there, and the cities value increases. Becoming a great trade partner or target of war far.
In the current system nomads and settlers are on pretty equal ground. Cities can be vacated at the smallest sign of danger because the place they are built on is the same as any where else. There is no motivation for taking the soil with you. A wondering player can grow wheat at the same proficiency and product as a 100 year old city-state located in a tropical oasis.
Nobodies going to want a small island in the middle of the ocean. That is unless it just happens it can grow cotton at 5 times the yield of the inland. Then everyone wants it and permanent settlement occurs.
If the farming and physical properties of soil differ, the tech trees and architecture of civilizations based in will differ. Nobodies gonna use spears and build out of sandstone and reeds with trees can be easily grown there.
In a world with biomes scaled up 20 times, trade, travel, and ware far will become real forces. civilizations will different in so many ways, there will be legitimate desire to set up a silk road between them. Under the assumption that chat is localized, city communication and politics will become real issues. Instead of a by product of a forced system of plugins.
This paired with some kind of system of ownership and rights over blocks that happens organically in the background, will help create societies.
This will also help when a bunch of people eventually want to customize everything about their biome (looking at you biome 'o plenty, and your hundreds of soil and rock types) and create archeology mods. We'll have compatibility all sorted out in our soil (and perhaps stone) libraries.
