It's not that everyone is changing to 940's. They are very good shocks, but there are other very good shocks too. From my understanding, the 940's have a spring on them that allows the shock, when a rider gets on the bike, to act like a 1" shorter shock...when sitting on the side stand, it's more or less the normal 13" height. The stock air shocks are pieces of chit in comparison to just about anything. The front fork suspension is as well. The front forks are like driving a '68 Buick with worn out shocks...mushy, extreme diving when applying front brakes, very poor response to the road surface. The stock air shocks are not that much of a hassle to adjust, but all the air in them is doing is adjusting the preload so they won't bottom out with a load on them. The actual performance of the shock is just piss poor. But, 90% of HD riders don't know any different, because they've never ridden a HD that has good suspension under it for comparison. You don't miss what you don't know about. Without fail, every single person I know that has upgraded their suspension says it is one of the best things they've ever spent money on...there is a night and day difference.
I'm not knocking any brand of centerstand. But, if a person designs a stand around the excessive Sag built into stock HD suspension for any given model, and the suspension is upgraded so that the Sag is less, then the stand will likely be too short. If there's a way to modify/adjust it, no problem.