I will try to provide a developing country perspective (Eastern European country - Romania). According to this source (Romanian) there is 5 year gap between retirement age for men and women (65 vs. 60).
I remember when it was announced and virtually nobody thought that it was not correct.
I think there are two major aspects:
1) High income families - they afford to externalize multiple chores such as laundry and cleaning, so house chores for the parents themselves are few and they can be easily divided between man and woman (gay marriage is not allowed yet). For this category, it might make little sense to have different retirement age. However, high income families are not many, so the vast majority of the families fall in the second category.
2) Mid-low income families - in most cases, most of the house chores are done by women (citation needed as this is based on dozens of first hand observations). Of course, house chores is also work, so women typically work more than men during their active lifetime.
Also, there is a strong tendency for parents to get help from grandparents (typically the grandmother) when raising their children, so people are quite happy that (often) the grandmother is available to help them in this regard.
I sense this might be true for other developing countries as well, but it clearly depends on multiple factors such a cultural background. For developed countries the other answers might be more fit.