Probably cost. If I'm not mistaken, before this, the short head does have a contact point for grounding. At least, I had never ever experienced any electrical short pre 2011.

After that, every time I use my mac with the short head in my office building - Lo and behold, always get the static shock thing. Probably because my body like magneto also (I am the only one in the family that gets static shock pushing Jusco shopping carts). Didn't took me long to realise that the short heads were missing the important grounding point, shame that I sold my pre 2010 with everything included, just so I can compare.