Those users that have those probably didn't want their precious armatar to be kept in storage, so they kept them on their page so they wouldn't get deleted.
But yes, I kept mine (as did many others), because I'm proud of it (did draw it, after all), and I thought it would go away when Carlie removed the holiday armatars from the selectable ones. It just didn't, but no one seems to know why.
How you ended up with one of Strop's, I do not know. Weird selection glitch. Must be some values in the coding that are the same or something like that...
Those people who kept their armatar after the halloween ones were taken away will still have the same armatar, until they decide to switch, in which they cannot use it again until next year.
The two new preview armatars however, are permanent, but there will be AP standards for them later on.
If what you mean is, you went to change your armatar and it didn't change, simply try again. It sometimes does that.
It is sort of a glitch, since the people w/ halloween armatars aren't allowed to have that picture anymore then they're reverted to the one you get when you first create an account (blank one)