A: There are several reasons we have heard about. Sometimes this reluctance is the result of religious conditioning in childhood which convinced the boy that "sex is dirty," and even perhaps that female genitalia are "dirty," unsanitary, etc. This unwarranted prejudice against women has prevailed for centuries and has often been perpetuated by the church. Quite likely it is the result of projection of the clergy's own mistrust of their own sexuality and lack of love of their own genitals. Hence the prejudice and conditioned disgust gets passed down through generations of males.
All that having been said, the reasons may be more mundane and immediate. I will always remember the first time I orally pleasured a "goddess" who had been into health practices, vegetarianism, yoga, etc. for many years - I was astonished to find no strong odor or salty taste! Her yoni was mildly sweet and fragrant. It completely changed my attitude about giving oral pleasuring. I became inspired! I fell in love with that yoni in a way I had never imagined possible. Since then I have had similar experiences. Just as healthy people smell sweeter, and vegetarians tend to have much less body odor and sweeter smelling skin if they are healthy, so too this applies to the "lotus blossom" of a goddess. Conversely, many men are turned off by strong odor and taste coming from a woman's vagina. They may be forcing themselves to hang in there longer than is comfortable, and not want to return even though they are well aware how much pleasure it brings their woman. I hope this question is incentive to many women to cleanse their physical body and clean up their diets. For most women there's nothing quite like receiving extended oral pleasuring from someone who is really into it and enjoying it!