Welcome to the second open thread on the Effective Altruism Forum. This is our place to discuss relevant topics that have not appeared in recent posts. Thanks to an upgrade by Trike Apps, each time you visit the open thread, new comments will now be highlighted!
I think old people just have more resources than young people, so they give less as a proportion of their resources.
Alternatively, you might think old people have had a lot of time to develop commitments to various causes, and so feel obligated to give more.
Back when I was involved with party politics, I heard someone mention that pensioners with basically unlimited free time were a really major asset for the campaigns of the older and more established parties.