Old women are useful
A theory I read, many years ago, is that the purpose of the menopause is to protect older women becoming pregnant because it is dangerous for them. Leading on from this, from the point of view of success of an organised society, it is vital to have a store of community knowledge - when to plant crops, what herbs are poisonous and which ones have antiseptic properties, etc.
Older, non child bearing women were the ideal repository for this knowledge and the mechanism for sharing it and passing it on; since they don't have the tendency (as old men did) to get killed while out hunting and fighting. The other advantage of older non child bearing women is that they do not represent a threat to younger women since the menfolk can't get them pregnant, hence they can move around a community freely, dispensing advice and useful gossip (or discussion if you prefer). Old men who try to wander round visiting young women for a chat are viewed with suspicion by everybody of course.
This is all old and ancient history and we modern humans are far more advanced and rational nowadays.