Btw, I didn't say I was grossed out by garden-variety May-Dec relationships, but by the newest wrinkle (so to speak): the grandfather/granddaughter pairing.
That said, I don't agree that just because something is commonplace, explainable and appeals to the participants, that it is fine, OK, or wholesome. Regarding the younger woman's motives for dating older men, there are two salient ones that I can see: a desire for Daddy because something is amiss in her paternal relationship, and above all else, an attraction to money and power. I have rarely seen young women go for poor, unsuccessful older men. While that might be "understandable," I think it's cynical. As for the maturity gap between men and women, it closes by the time most guys reach their mid to late twenties. But if a woman does feel that the guys her own age are immature, why not date a man five years older? There's plenty of room between your peers and your father's friends. The litmus test is, if your 25-year-old daughter were involved with a 45- or 50-old year-old man, would you feel OK with it or distressed?
As for men's motives, once again they're explainable, as in "you're as young as the skin that you touch." But are they commendable, especially when most of those men have discarded wife number-one for the younger version? While I understand their motivation, I find it pathetic and have infinitely more respect for men (like Paul) who can be with a woman of similar age.