Well, since you asked, there could be a hundred reasons why he (we) decide to go from the left seat (or right seat, for that matter) to the back seat.
1. Poor financial planning
2. Supporting his previous 3 or 4 wives and their homes
3. Wanting to stay "connected" to his previous life of 30 years
4. He feels too young to retire
5. Likes to visit friends/places around the country
6. Hopes to get back in the left seat with the Age 60 rule change
7. Still feels he has something to offer
8. Enjoys the lifestyle he has become accustomed to (being on the road)
9. Likes the smell of jet fuel in the morning
10 Because the Company allows him to stay
11-100 And any number of other personal reasons that are none of your business.
Although once a captain, always a captain, I do wholeheartedly agree with Jack Lewis' dictate to wear the stripes of the seat that you are occupying. It's purpose, I'm sure, is to eliminate confusion. Not within the cockpit, but between ground personnel and crewmembers. After all, if you walked in and saw this distinguished, older guy and two young snot-nosed kids
, whom would you assume to be the captain? So wearing the 3 stripes helps eliminate those types of issues, and I'm all for that.
As for the pay. Same thing. You should get paid for the job that you do. Plain and simple.
The bottom line (IMHO) is this: guys go to the back seat for any number of reasons. All personal. If they do a good job, great! If they do a crappy job, then they should be somewhere else. Just like any other guy flying an aircraft. If you don't like it...tough, they didn't make the rule, they are just living by it. If it effects your quality of life, live with it. You'll probably have the same capability at some point in your career, if you decide to exercise it. In the meantime, you might think about the fact that if not for that guy, you might not be where you are now. As an example, if not for the original guys shelling out of their own pockets for gas, this company might not even be in existence now.