Around where I live geothermal is used more for schools and large office buildings than by someone's residence. I can't say that is the way it is all over Wisconsin, but in my local area that's how it is. Having said that, there are a handful of houses that do use geothermal, but that is the exception rather than the norm.
I am not sure why geothermal isn't used more for homes around here, but I suspect it is due to the initial cost and possibly available space. Also, the cost of natural gas has come way down so people who have natural gas available to them are less likely to be willing to spend the money for geothermal.
I know it was talked about by the local City Hall to put in geothermal for some of their buildings, but that's where the idea ended, in the talking stage. Not sure why the idea was abandoned, but it was.