Me thinks it's the guys with only 6 inch long dicks that give deepthroating a bad experience for women. If he was shorter, it would be just in the mouth, and if he is longer it will tuck down her passage. But it is that unfortunate median length that ends up triggering her unpleasant button. Also, more importantly - she could have a "virgin throat", and sometimes it requires a man's initiative to pull her head down all the way. You might be nervous to do that, especially if you are only dating or less, but if she already knows how to comfortably throat a big cock, another man has gotten there first, and most likely he helped her.