Mainly because they seem to be the in thing to moan about at times, ie 1 starts and 50 or so people then seem to have blue badge issues.
Plus in the years I've had on this earth I've yet to witness witness any issues with blue badge users, nor as a blue badge holder have we used it to park on the roof of a double decker.
I'm quite an open minded cheese too, I even witnessed a scrap on a bus once.......but that's the risk I take when I use the number 3 
I dunno, I just have visions of a load of wild haired harridans, red eyed and foaming as they tap out a ad of bile fuelled by yet another sleepless night thinking of people who have something they can't have, driven slowly mad from years of adding up blue badge holders saved parking charges and playing spot the badge adorned car on the double yellows. 