My take on it is that people in general, not just aging men, have a seemingly bottomless capacity for self-delusion. Dave Barry once wrote that a man can have a gut big enough to hide an aircraft carrier and still consider himself a borderline Don Johnson (Jake Gyllenhaal to you kids today). He thinks that a young woman would be interested in him because he's generally right. The supply of inexperienced, insecure, and generally impovershed (not poor but not making the kind of money a much older man can afford to lavish on her when compared the guys her age) young hotties is plentiful. A guy who comes in with even a modicum of style and an appearance of financial wealth can impress them enough to bed them for a while or, in some cases, snare them into a long-term relationship. For some girls, especially those from divorced homes, the older guy is a surrogate father figure. Lastly, there is a bit of hardwired biology in play. An older man more capable of providing for young girl than young guy is subconciously more desireable, up to a certain level in some young women. That's how I see it. I can offer no scientific proof or study on the issue.

Maybe because that lump in his pants turns from an erect penis into a wad of cash as a man ages.