I live in Chicago and have family in Chicago. So I do not NEED to track another time zone by any means. BUT - the jumping hour hand could not be more useful when I'm on vacation in Florida or California, etc. This functionality is amazing for a quick change of the local time. I usually keep my GMT hand on London time simply for admiration. I do, however, use the bi-directional bezel quite a lot when cooking or when I've parked on the busy streets of Chicago.
So - am I flying a plane across 5 time zones and do I need to track 2 zones at once?
No, but I have sincerely enjoyed having a GMT on hand for the past few years (I own 2... a Tudor GMT and Rolex GMT Master II).