Prologos, you do have a point. There are many cultures in which the practice of young women marrying older men is quite common. The older man satisfies those young women's need for security.
However, where this becomes problematic is that the union may benefit the two who married - the older man gets a nursemaid in his declining years and the young woman gets security far faster than if she married a younger man who still has to accumulate his wealth. - but the ones who pay the price are the children born from that union.
I have met a few people who had an elderly father. Their fathers were elderly - over 50 and more - when they were born. These children often miss out on what other children have - a father who engages in sport and play with them, and quite often, that elderly father is already long gone when it is time for them to mark their rites of passage.
Not only that, but grandchildren never get to benefit from the wisdom of the grandfather - he is long gone before they are born.
December-May relationships work well for the two who decide to hook up - but not so well for the children.