In our culture, dating an older partner is often seen as a status symbol for younger women — we're often told that older partners will be more financially and emotionally stable, which is why being courted by an older partner is often seen as a compliment, a confirmation that you, indeed, have your act together and are desirable.
This is probably why heterosexual women's age preferences in partners tend to skew their own ages of higher (while heterosexual men's tend to skew younger).
For this reason, being a woman with a younger partner is often viewed in a negative light. We can fight this totally gross line of thinking by agreeing to view younger people that we have chemistry as real possible partners — and by not constantly "joking" about any woman we know who happens to have a younger partner.
You're supposedly an immature doofus who can't attract partners your own age, or maybe a delusional narcissist who can't cope with aging (I've heard both! Again, all these ideas are based on stereotypes — primarily, that youth is one of the only valuable traits a woman possesses when dating, and that to take a pass on using it as a bargaining chip to find a more desirable mate is insane. (But, of course, if calling yourself a "cougar" gets your rocks off, then more power to you, my friend.)There's another myth out there that dating young people means that you'll never get serious — that dating a younger guy or girl means that you're signing on for a relationship purgatory full of half-assed plans, a lack of emotional commitment, and being introduced as "this girl I'm kinda hanging out with" at parties.
When I met my boyfriend Jesse, I was 28 and he was 24 — not too much of a dating age difference in the grand scheme of things, but to hear some of my friends at the time tell it, you'd think we were Harold and Maude — or at the very least, Ashton and Demi.