It's a 'thing' here (US) called 'Silver Separation'. Some are mutual ('we stayed together for the kids') but most aren't. I wouldn't say it's only women initiating it, but I do think there are many more women than men who do it for 'incompatibility' reasons as opposed to the man turning his wife in for a younger model or to go off and 'find himself'.
Of the women I know it's been driven by the man or both of them approaching retirement age + the 'empty nest' (for those with kids). Those women look at the 'man in their life' and realize with the DC grown and gone when retirement comes that man will be around them and/or the house 24/7 and will have no other focus but the house and the yard, what and how she's doing things and why. The little things that drove them crazy about their husbands but were tolerable when they worked full time and only saw each other a few hours a day and the weekends loom large. And they realize that they don't want to deal with it and they certainly don't want 'work on the marriage'. They feel they've been working on it their entire marriage with no result. They are d.o.n.e, DONE. And in all the cases where the woman left for that reason, the man has been absolutely gobsmacked and 100% in denial of the reasons why.
I don't think it's menopause and it does a disservice to women to put the blame on 'hormones' or give them as a reason. Men have been doing that since time immemorial, we don't need to add to their validation of it being a woman's 'fault' because, you know, hormones. It's that women get tired of men's shit and realize, in their 50s, 60s, 70s, that there is more in their rearview mirrors than ahead of them on life's road and they want to enjoy the rest of the journey. And that has nothing to do with hormones or the menopause.
An equal phenomenon is the many women who have been in happy marriages who decide upon widowhood never to marry/cohabit again. The marriages have been good and their husbands kind and equal partners. There has been true love. But they realize that although the 'bonds' of matrimony were happy ones, there are distinct advantages to having no bonds at all.