Because the practices break down soil organic matter which help stabilize the soil.
The American Dust Bowl was a combination of things, but the frequency of tilling was a big part of it. Farmers now till at least one fewer times per year, which makes quite a bit of a difference.
It's complex, because our annual crops are almost all prairie soil plants, prairie soils are typically bacterial dominant anyway, but fungi typically provide a lot of the soil stability. Tilling pretty much kills all of the fungus, and the bacteria run wild breaking down soil carbon (fungal and crop roots).
