I have a theory on it based on some experience plus talking with girlfriends and such.
See, it is one of the things truly learned mutually.
A girl cannot "practice" and find out what she likes most and doesn't like etc.
Not like with masturbation with fingers and vibrators and such that can help tell her partner what she needs.
Until finding what is just right for her, and with all of our sensitivity and hot spots being different it is truly do the best you can.
And if it has not happened yet, it gets frustrating to just keep going the longer it takes.
With guys, everything is out in the open. I know it is why I love giving oral. I can experiment and try so many different things. And with everything on the outside, there is so much to explore.
With receiving oral there is really not a whole lot to work with unless he uses fingers and/or toys in addition. But, I do enjoy it, it just is not my favorite thing.
When I do enjoy it, it is all about the tease and build up. Boyfriend does not even touch my clit until I have got insanley hot with teasing. That is when I have orgasms with oral.
If he gets there too early, it is not as enjoyable. The orgasm happens, but the intensity is very low that it feels almost like half an orgasm.
If you like giving oral, perhaps 69 is the best thing.
It gives you something to do while he is having fun. You might be distracted enough from what he is doing to not have the worries and concerns or being anxious or as Paige mentioned, not worry about confidence.
It might be just the thing to relax you enough to where you enjoy it enough to find out what works for you.
amber