Hi Roger from Baltimore,

To answer your question of the "Why" of altered tunings--and I'm not trying to presume that you don't know, or haven't thought of this. It isn't the "lush sound of open strings ringing the same note" as you described. It is the accesibility to close intervals that is otherwise impossible (or at least improbable). It is the capability to mix slide with fingerstopping. It is the capacity for notes lower than standard tuning (open D,C etc.). It is also to solve the need that many soloists have to be their entire accompaniment and wanting a fuller sound. There's also an alternate tuning "culture" that has developed and, though as I mentioned previously, I'm not a huge user of any of them except drop D, anything that gets more people interested in, and playing the guitar is, to me, a good thing.
As an aside, the upside down kyser gets in the way, as mentioned by midchick, takes FOREVER to get set that way, and, because the back piece of the capo grips so little of the neck when clamped that way it goes FLYING off the neck at the most inopportune time!
Humbly submitted,

John