Jim the reason you do not see any reasons given for we need to define atheism without defining the scope as well is that nobody has even suggested that  You know what else you dont see any reasons given for  You dont see any reasons given for using giraffes instead of horses to pull carriages  Nor do you see any reasons given for wearing shoes on your hands instead of your feet  I assume youre not doing this intentionally but youre making whats called a strawman argument and its not the first time youve done it  Please be more careful as logical fallacies whether deliberate or accidental in addition to irritating others tend to impedeobstruct progress and i assume in good faith that neither one of these is your goal