Relatively recently, primarily as a result of all the crafting I do, I came to the realization that there are quite a few advantages to being a member of the Ul'dah GC as opposed to the one in Gridania, (which is the one I am presently a member of) or the one in La Noscea. Among these advantages are:

A MB right next to the retainer's summoning icon, the ability to travel to other worlds much more easily (which is quite handy for searching for the cheapest prices to buy something that is expensive), and the ability to easily access the GC HQ.

If I understand everything I have googled about changing GC's, not only do I have to reach the rank of 2nd lieutenant to do so (I am presently the lowest rank required to make special deliveries (Sgt 2nd class), but, once I do, I have to start out all over again, just as I did when I joined the GC I am in now, completing hunting logs, and doing leves and fates to gain the seals necessary to once again reach the rank of Sgt 2nd class.

Which leads me to this post. If the above is correct, why would anyone undertake the time consuming process of joining a different GC than the one they are currently a member of?