Work is transformative. It gives you a greater chance of a greater income. You can affect your life while you're of working age so you have scope and opportunity. Pensioners do not.
Age is the first limitation on roles that I've ever had to encounter and I hit that awhile ago.
Middle age went by while I was mourning for my lost youth.
While one finds company in himself and his pursuits he cannot feel old no matter what his years may be.