It all boils down to;
Why do people play this game?
Why would people quit this game?
And where does XP locking fall in this equation and how does it influence a person's choice of whether or not to continue playing the game?
If you would like to discuss specific points, I'm all ears. The whole idea is to spur discussion.
I make no claims outside of "This makes a helluva lot of sense to me". I also do not claim to be quoting any specific person or source.
Which reminds me...
I'm still waiting for a source for this little gem.