Older men and younger women have two very different social circles. They have different friends and they hang out with completely different sets of people. This makes it easier to keep the relationship under wraps and act with secrecy. This may be a favorable situation for both the parties and hence the prevalence of the behavior.
#6 Younger women are more flexible
When it comes to sex, younger women are way more flexible, both in terms of attitude and their bodies. They can be all right with things that older women would not be. They can be open to practices which older women would not even consider. Older men, therefore, go for younger women to achieve fantasies which they may not have lived with older women.
#7 Much less work
The older man, in a relationship with a younger woman, may not have to bear any responsibility. He need not be emotionally responsible for them nor do they need to worry about long-term factors. This, in a way, breaks him free from a lot of responsibilities and work which he may have to put to date an elder woman. Easy, therefore, may be one of the biggest reasons.
#8 Lesser responsibility
Younger women may still be looking to find their feet. They may be looking at options in life and may not get emotionally attached to men, in most cases. This no-strings-attached scenario is a win-win for both the parties and it does bring them together for an affair or a fling which may otherwise not have been possible.