Because "you can". When you move up in license class and get new privileges, of course the first thing you're going to do is exercise them. A vanity call sign is just a small part of the bigger equation.
When I first got my callsign, KD5OWO I always said I wouldn't change it, it felt like mine. The issue I found was that after I got into contesting I found that having the shorter callsign was going to be a big advantage. The choices were fairly limited but I wanted a call that sounded good on both sideband and CW if I decided to operate CW. KJ5T was a good choice, now I have had it longer than I was KD5OWO. Who knows if I will ever change it if I end up living "permanently" outside of the 5th call district, I have become quite fond of the callsign.
I can only conceive of ever changing my call to what was once a family friend, now more than a decade SK. It was a 1x2 and he was the original holder of that call. It is merely a sentimental/nostalgia issue to me as I don't regard it to be a particularly good CW call, though that was all he used it for. Given the state of call hoarding, it is quite unlikely I would ever have a chance at it. Although, should a certain 2x2 of another associate of mine ever become available, I might consider taking it on for the same reasons above.
OTHER.....When I was a novice (WN8AFS) all the good ops were long time hams with one by two like W8FX (who lived a mile from my home). When I upgraded to the Amateur Extra ticket I was elegable for a change and got K8(my initials) for a new call.
I got a vanity (1996) just for CW. N2UQF also sounded horrible when spoken aloud. No regrets. Many might think I got a vanity to play oldtimer, but it's really for the dits and dahs. 73, Jordan AB2T
Since I don't contest, I don't see it as having any real world advantage for me. So.... I don't feel the need to have one. However, I'm neutral on the subject of short call signs for others. If a person has one, great. If they don't, it's also great.
You can accomplish this "phenomenon" with a 1x2 or 2x1 by simply waiting a moment before transmitting.
