Just as there is a lot of wisdom to the meme, "don't marry too old", there is also corresponding wisdom to the opposite, "don't marry too young". With young women they will experience serious FOMO, or, Fear of Missing Out. Never underestimate how powerful societal pressures are.
In the old days you could marry young because the social environment was such that it was expected and encouraged, now, the woman will be worried she's missing fun in college if she marries a high school sweetheart, and finally she succumbs to curiousness.
Another example is military relationships, you should not enter relationships in high pressure, high mobility environments. Anyone who has spent any time around military types will know the military has a huge cheating culture, which is exacerbated by deployments, and men coming along to the women that are always more "alpha".