To add more to the argument.
With advancing technology comes better clothe, shinier watches, faster sports cars, bigger mansions, more expensive consmetics, and many others. . All of these help increase the value of the person that increases the attraction. These luxuries cost money. So the person with a lot of money has a huge advantage in the reproductive process. To make alot of money in society a person needs to have intelligence, that incluedes intellectual intelligence and emotional intelligence. Intelligence compared to physical ability has been a bigger factor in survivual and mating than in the past.
Being good looking, tall, and strong helps you to get laid. But, knowing how to dress, how to speak eloquently, and how to game women; along with the ability to to afford nice accessories like nice watches, cars, and others will increase your attractibilty much more than merely being physically attractive. Many of the latter attributes requires thinking.
//*It's weird that we use primital instincts to determine who we're attracted to. In ancient times your physical attribute was pretty much what you were. You either looked good or you don't. But many of these things can be manipulated nowadays with clothe, cosmetics, surgury, hair gel, and others. maybe we still prefer these from old animal days.*//
Also, with the advancement in transportation and technology people nowadays are able to contact and meet many more people than in the past. Our expanded social network allows more options and benefits the most attractive ones by natural selection. We may even mate with people from different regions, continents, and even...we're not quite there yet.(yuck! If they are like the things on TV, never.) In the past you probably would try to get the most attractive person from your village or tribe.
Example- NBA players who are physically gifted benefit alot from modern society because almost everybody now knows what the league is and how big of a deal is to play professional basketball. The big audience brings big revenenes to the league and the players get high salaries which makes them young, physically attractive, and super rich so it's no surprise why they have sex so often.
The last reason I think is cultural. In the past many marriages were arranged by parents, women married at a early age which leaves less time for dating and selecting, and women were timid of contacting men in fear of pregency. In recent times our views of dating, sex, relationship, and marriage have changed dramatically. We try to look for love which is largely determined by value and we date more, marry later, and have sex more. These things all help the natural selection process. The arrivual of condoms, pills, hollywood, drugs, cheap liquior, and others(thanks to modern tech and methods) have helped provide grounds for the cultural shift to take place.