How has our ability to drill deeper wells impacted where humans can live?
Not to any great extent, with some exceptions.
Most deep wells are related to oil and gas exploration and these tend to be away from major urban areas. But the depth isn't that critical - its just that oil and gas wells and urban areas just don't mix - at least in North America. I visited an oilfield in China once wherein there were active pump jacks pumping oil right in the middle of a town!
The other emerging issue that is creating conflict between oil and gas wells and urban areas is the drilling/extraction technique called "fracking". Fracking has caused small earthquakes close to urban areas and some communities are calling for bans on fracking.