The real deal is that many simply can't afford to retire right now.
Remember, UPS has only operated their own airline for just 14 years now. We lived with below industry standard contracts until our current one which still lags in retirement. Many of the "retreads" came from now defunct airlines such as Braniff and Eastern and some went through the Continental strike in the 80's with Lorenzo. Many of these folks lost EVERYTHING and had to start all over!
There are also a select few who have a couple of ex's and/or kids in college, made bad investments, didn't save enough etc, etc. who simply just need the money. They're making $100,000+/yr and have pretty good seniority when they go back to the panel. Heck, they probably fly better trips sitting there then when they were Capt's.
I think after our next contract, which is amendable at the end of 2003, and retirement issue being near the top of our priority list, you'll see many of these folks retire.
And that, they say, is the rest of the story.