So, this is just my
experience in the matter.
We find a couple scorpions a year inside the house, and a few outside the house yearly as well. I'm on the edge of the desert outside Tucson, so wild areas are nearby.
The things that have made scorpions come into the house have been destruction of their homes OUTSIDE the house, because then they start looking for new places to live. This happened when our neighboring property dug up their property to build their house. We had more scorpions in the
yard then.
They also follow the food or water (they require actual water sources and do not just get it from their food, like some other desert critters). So if there are insects in your house, the scorpions will follow them in. And if they cannot find water sources OUTside of the house, they may look for them inside the house. Keeping insects out of the house seems to keep the scorpions disinterested, at least in our case it has. Each time we found scorpions in the house, we were finding an increase in other insects first. We also have an outside water source, so that may make a difference.
In re: to soil changes eliminating the scorpions? I think that it actually might, or at least lower the population. I find the scorpions in our yard under rock or brush in the areas that are still more desert-like. I have not found any scorpions in the areas that now have more moisture retention (but not pooled water). It doesn't seem to make an appealing home for them.
However, if you can tolerate them, they do a pretty good job of killing some of the insects you DON'T want around. Some of the bigger ones will even kill rodents, which for me is a huge plus. I think a huge nest would be an issue, but if it's just a few out in the yard, they are actually pretty easy to get along with as long as you aren't walking around barefoot (and really, in the desert, you're usually not). I just note the couple of rocks they are hanging out under and we leave each other be.
Oh, for protecting the house from 'em, possibly
diatomaceous earth might be a potential solution.