The bottom line is that servers on earth is not as scalable. Solar isn't as available on earth, and trying to tap into what is available will probably lead to massive habitat destruction. Heating homes with the waste heat makes the heat harder to remove (you have to pump heat, which produces heat), and would require infrastructure that is costly to build (e.g. water pipes). Space is colder than liquid helium, though it does not directly conduct heat (you have to use black-body radiation).