Just because roofs weren't being measured doesn't mean it wasn't obvious either. Cost-effectiveness would have a decent bearing on things.
Aerial mapping, up until not that long ago, was really only readily available via commissioned contracts/flights .. see government or military. The average roofer didn't have access to imagery that would have been cost effective. But you can see a roof from the air. Duh.
Even 10 years ago the average punter wasn't accessing aerial imagery. You would have to go to government or the odd private supplier and see what imagery they had, buy a print. The internet has helped.
Surveyors and mapping groups have been measuring from images in 2D and 3D for decades .. I still remember playing with a stereoplotter in the late-70's early 80's .. I would have been under 10 years old.
Since then computers have helped .. I think even ERDAS Imagine had 3D measuring.
