Hey Mayday,
It's really not important that you understand them. It's only important that they understand themselves, and what they elect to do with their lives is their business, not yours. I understand where someone would pass judgment, based on their own likes and dislikes, but that doesn't make it right. If a guy wants to work past what you consider a reasonable retirement age, that's for him to decide. Hopefully you can understand this. If not, then there's no hope for you at all in the context of this discussion. Best to you.
JJ