While he certainly does not need the money, I think that he love and feeds off of the energy of the audience and realizes that his performing for 2-3 hours is supporting a very large community of workers from the band, roadies, stage managers, venues, gift shops and popcorn vendors.
But health (for not only him, his family, and entourage) has to take priority. Travel at that pace has to takes it's toll on an 80 year old man, usually leaving his wife at home, living out of a hotel.
At this point, he has many children, grandchildren and great grandchildren that I expect love to be around him. But I also agree that he is not the type to go into retirement. While he might stop touring, he will continue to write and record until he drops.
I had the incredible honor to see him with the Beatles in 1966 in Memphis and 4 other times solo and Wings, the last being in San Francisco when he closed out Candlestick park. Through a fluke, we bought tickets in the nose-bleed section but were nice to a few people and got moved to the front row 
My fantasy, and might say dream, is of course, after 50+ years listening to this amazing man create love through his music, including watching the Ed sullivan show in 1964 on TV, to meet him and shake his hand to say 'thank you'. Would it be too much to ask for a quick fun jam session, two musicians kicking around ??
Anybody got connections to help me fulfill my fantasy/dream ?
Wishing Paul and all of his family long life and lots more of music !