It can take 10,000 years to create a good soil layer. The more weathering, the more soil. Soils move downslope. They are less thick on steeper slopes. This is the big one.
Soils differ significantly between arid, temperate, and tropical climates.
Basically it comes down to differences in the amount of rainwater, and differences in the amount of humus. If more rain, one also gets more plants, and potentially more humus. Dying plants can supply organic matter to the soil, which can turn into humus. Lets build a table to look at the relationship between climate and soils. This adds humus to the soil.