As crazy as it sounds, it's more of a usability thing. The previous name is so long that on a narrow screen - such as my iPhone - it collapses the Inbox and Alerts menus into one. So to see my alerts, I have to press the combined menu, then I have to press Alerts, then I load the full Alerts page and then I can finally see all my alerts. So, yeah, I changed my name to save a couple of clicks a day 
Also, how long does the "Formerly [Name]" user title stick for?