I don't think there's anything for them to tell... or nothing for you to learn anyhow.
I meet girls who hate giving head. doesn't make sense to me either.. asking them why only means I'm going to hear a dumb response.
Some guys I know don't like it because of bad previous experiences. Some are just grossed out by it. But I don't understand how you are grossed out but then can have sex.
Girls I know that don't like it don't think its gross, they just don't want to do it. Most of the time the reason is because they are getting nothing in return.
Most girls don't mind giving head, but Ive only met a select few who LOVE it. It seems like there are a lot of guys who LOVE eating girls out, so I thought there has to be some reason if they don't like it.