What stops them is that every person with some experience knows it is a stupid idea by thinking 5 minutes about it. I guess you could give it a try by playing the advocatus diaboli and coming up with a list of costs and problems a space data center has, that are rrivial on earth. You know, all the stuff they skipped in their fancy pdf.
Then you read this thread where tou will likely find more, that you didn't think of. That is a good lesson if you need one.