As an expat I see this in the extreme very often. When expats talk about the ages of there wives / GFs they usually refer to the years of separation between them. Numbers like 20. 25, etc. are common, some are more, 36 is my current.
But we live in worlds that are often torn apart and where families are relative. Most women either don't know or dislike their fathers and that has a great deal to do with it. They also have had few if any good experiences with the local men.
Add all this up and the answer is stability.
My parents ask what on earth I could have in common with such a young woman? But move to another country and you have nothing in common with anyone of any age.
My personal experience is that every woman I've dated over 40 has too many issues and too much baggage. It’s not that they have it, we all do, it is that they open it every day and live in it.