Heather you'd want a masters in psychology to figure out some of the people on here. My personal views are this.
Escorts.
Possibly they're genuienly retiring and announce it to drum up a last bit of business. More likely I think the escort is about to change identity, again, and wants to also drum up business while the new identity may not be linked to the old because everyone knows the old one retired.
Punters.
Possibly genuinely quitting and has formed a self esteem dependency on this site. On E-I they see themselves as important people of significant standing. As they leave they want that affirmed so they can be confident of their standing. They make a grand announcement so they can have their standing rubber stamped by other posters as they leave because that's important to them.
On the other hand, you get punters with brain wiring issues who go and then come back as someone else. Raising a thread about the departure is like being able to hear what's being said about you at your own funeral. This type of leaving poster is caught in a revolving door ... will always be coming and going at the same time.
There's enough material on this site for ten Phd's in social sciences and psychology.