There's more than one reason older women are more attractive these days: not only because they've been taking better care of themselves, having less children, and generally living their lives in more fulfilling ways, but also because the biological focus has shifted more towards present group maintenance rather than future sustenance of the species as a whole.
As we near the visible end of the human adventure on earth, the identified "instincts" to propagate give way for more reasonable and practical instincts: how to live well the rest of the time we all have left.
The saying that males -- young and old -- are always on the lookout for the young, fertile females as an irrefutable, irresistible urge to carry their seed into the far future, may be shortfalling to a new reality of a species in precarious conditions of survival into that far away future. Chances are getting slimmer daily that even two generations from now they will be able to enjoy simple pleasures such as non-toxic shellfish, or un-synthesized meat or natural plant and fruit products. Bladerunner comes to mind, with a now more plausible scenario of most animals being extinct, and a huge market for animatronics and synthesized hyperrealistic creatures, used in everything from pet needs to natural photoshoots for visual illusion.
In biology, animal species tend to propagate in different patterns mostly according to their environment. In a high risk, dangerous habitat species reproduce in quick, large quantities, flooding the environs with as many offspring as fast as possible in the short time of parental life they may have left.
Seeing how we -- and I'm primarily talking about middle class western societies -- have created a more comfortable environment for ourselves, with most people working with an option for windfall for future needs -- savings plans, 401Ks, the need to reproduce no longer serves our environment. Although we are still in need for a young workforce to maintain the older crowd (which is getting older by the minute as baby boomers age) it is no longer true that having more kids is more profitable or even convenient. Women in these countries are in fact discovering that having any kids is not only quite unprofitable, but downright inconvenient to the simple goal of having a happy life.
Both Italy and Japan have continued to hold world records in negative population growth in the last ten years. Despite minor differences between these two countries, within the same socio-economic status child-bearing women have largely stopped having kids. Women's lives have simply been made more difficult by having children, apparently at all socioeconomic levels, so women have finally stopped and taken note. Females are not moving out of their parents' house, not getting married or just choosing to not spawn even when partnered. It's simply too much trouble -- and not enough reward. There is the highest level of single female headed households in the world now than ever before, and a higher number of physically self-sufficient women than ever before.
In this present-tense scenario, people look to sex more for bonding and entertainment purposes, and for raising the quality of life. The whole esthetic of bio-fertility of younger women being more attactive no longer makes sense, and it's resulting in males opting for older women rather than young ones as a more attractive choice. I don't believe that these are conscious choices, but most talk about children as a major motivator for relationships no longer holds true nowadays, for the vast majority.
