Because if you change it to Justice League United #14, then the uninitiated will be wondering what happened to issues #1-13.
I never understood this argument, especially in the age of the internet.
Were people confused in the 80's when The Fury of Firestorm The Nuclear Man
changed to Firestorm the Nuclear Man
, and then to just simply Firestorm
during it's 100 issue run?
Did people back then go rummaging through their comic store's bins looking for Adventures of Superman
#'s 1-423 and then become even more confused when they couldn't find them, but Superman
, which had a new #1 issue, also had up to issue 423, which had been published recently?
What about fans of Justice League
, which became Justice League International
with issue #7 and then Justice League America
with issue #26, just as Justice League Europe
Hell, nowadays, the change from Flash
to The Flash
between issues #100 and #101 back in '95 would be cause to relaunch the title at #1.