This may not apply everywhere, but around here (Saskatchewan), retirees are the lifeblood of service and community organizations. From the quilting club that generates revenue for brain injury research and food banks to the senior centre that helps people age in place, retirees are a critical component of the glue that holds us together.
Even if you have a fairly narrow economic view of what it means to contribute to society, there is no question that retirees are making those contributions. While actual money is required for most things, nothing happens without people putting in time and retirees have plenty of time and aren’t shy about using it.
This is something I became aware of as my older relatives retired. Now that I’m retired myself, I’m more active than ever in the community, despite having also retired from the volunteer fire and rescue service.