Barbies

Can anyone please explain to me WHY is it that 6 year old girls are always having the Ken kissing Barbie? I have always noticed that when Anna play with her Barbies they are always kissing? Since Anna is our only daughter I haven't thought much about it, until today, Anna's friend Viktoria is over for a sleep over and I notice her playing with the Barbie's and GUESS WHAT??? You got it she too has Barbie and Ken "making out" what is going on here?
I wish I could say that Eric and I kiss / make-out in front of our kids daily, but that seriously isn't the case! So, where are our little girls learning this? T.V. maybe, movies maybe? If anyone one know more about kissing barbies and 6 year old little girls I would love to know.