Historical Trust?

We came across this place and discussed amongst ourselves, why they had left the old front wall of the house in-place. The only conclusion we could come-up with was perhaps that the local Heritage Trust had insisted that the front of the building was to remain, (not sure why or what significance it had), so they knocked the rest down then proceeded to build the rear.
The thing is, the rear building looks almost as old as the front.
We have seen lots of construction, simply abandoned. Some of it like this, that must have stopped 10+ years ago.
The bricks intending to close-in the top floor were left up there - it looks like the workmen simply walked off the job and never returned, very sad, but one of hundreds of houses and businesses along the Camino.