It costs less to run new electrical or plumbing to an attached garage, especially where those features connect with existing lines. For instance, if you want a garage with an apartment ...

The Faith Mission and an attached vacant building in downtown’s Discovery District will be redeveloped with a mix of loft-style apartments ... to a 31-space parking garage.

You realise that your loft is actually prime storage space ... Use your garage If you have a garage, attached to an older house, then chances are it's too narrow to fit a modern car.