How can I say it...
What makes feet and legs interesting to me is that they are close to the "prohibited spot".
I think touching the feet and legs teases the girl (especially if she is inexperienced and / or shy), it is increasingly near the forbidden spot.
If it is clothed, is to avoid touch, but that does not hide the desire of her.
As we are talking about innocence and shyness, cute feet are the best =3
Now that feet are a appealing spot, making it grow, especially in young and shy girls ir really a turn on ^^