Ruins being rebuilt

          When I was growing up in the Scottish Highlands there were many many ruins. All sorts of ruins from castles to crofts, the countryside was littered with them.
         Now when I go back and visit my mother (still living in the same place) I see, to my amazement, that not only have the ruins become smart, new lived-in houses, but there are also lots of new houses, where before there was nothing.
Now - this is all very splendid and I am very pleased
But - what do all these new people do?
        There is very little new industry and crofting is dying. All I can think of is that everyone must work in a service industry of some kind and they are all just working to service each other's needs without anyone actually doing something productive. Possibly not a sustainable model?