As always, it boils down to cost. The SFA can't afford it and no government will ever fund it as it's a guaranteed net vote loser. We had an opportunity to move to a new stadium when Hampden was redeveloped - I even remember talk of relocation to a site in, or close to Strathclyde Park (as there were good access in and out), but that ship sailed and we are stuck with the "new" one.