We're talking about goods with a target market strongly saturated with women. It is therefore a given that there will be at least 65535 permutations of product variables, for each brand.
Your dad didn't want to (attempt to) buy you tampons from the store because it would probably take less time for him to extract raw iron ore from your backyard and build a tampon-making machine for you, with his bare hands, than it would for you to describe exactly what you want.
Given his quickly fading memory, the probability of him remembering your detailed instructions is low. This combined with the possibility of an embarrasment factor, and the thoughts of deadly force which will surely be exerted when he inevetably returns with the wrong product, probably quickly led him to make up his mind and not take on this challenge.
"So was that Tampax tripple nibbed with ribbed applicator and streamlined profile for fast insertion in a blue sky textured attractive 10 pack with a moon on the reverse side? Is the heavy flow option mutually exclusive to the 7 days of the week night and day Poisson Distribution statistically modelled flow variance with picasso box art? Would you like fries with that?"