I think you neglected the factor that flow varies over the course of a period with a shape like sin(x) from x=0 to x=3.14. Or in other words it starts off slow, peaks, then peters out.
Being a woman, yes, I am entirely aware of that. Unless you have a single day where you're pushing out two tablespoons, though, which is very unlikely, my point still stands.
And many women go through 3 pads a day during their peak. Which is much more convenient than having to change your underwear, and have somewhere to put them to carry them around with you until you get home.
Those "many women" may have menorrhagia and should consult with their doctor for treatment, yet very few realize this and just think they are "heavy flow" people, which puts them at risk for disease and other medical problems. I should think, though, that it's much more convenient to carry around one pad than three, and for the rest of people is probably a relief to not need one at all.
