Why Do Most Women Think, their past (i.e their sexual history) doesn’t/shouldnt matter to the man they are currently Dating?

Not a grand eternal truth--my opinion only: If the past is an agreed upon subject for both to disclose, then okay. But make sure you don't out outdo him on the details. Save that for revealing your fantasies. Or better still, tell your past as though they were all fantasies. You'll get the self-satisfying feeling of "coming clean" and he will be thinking what a fertile mind his wife has.