That is one of the worst insulation jobs I have seen. 
They did it over the door and window headers as well.
I think Scott has hit the proverbial nail on the head.
Without a doubt. Worthless would be a better description, terrible.
I agree totally. Useless by all means.
It appears the framing contractor and the insulation contractor are “one in the same”.
Make you wonder how many homes end up with crap like that.
Probably a lot. It helps explains why a lot of inspectors IR cameras light up when they’re inspecting newer homes and find a lot of voids at the exterior walls.
In addition to the insulation / r-value illustrated in Neils picture a doubled stud wall is useful for sound dampening - like for privacy between Mom & Dads bedroom and the kids room or in a recording studio. I built several sound-deadened rooms for recording / audio control rooms “back in the day” for broadcast stations.
Typical framing for the shared wall separating a duplex to dampen sound or to allow 2 layers of sheetrock to increase fire-rating. That is what I have seen it on plans for.
That is what I have seen it on plans for.
And they frame the extra 2x short of the top plate?
None of those circumstances apply on this house, thats the head scracher!!!