I guess it's how you shoot, or maybe how you feel about how you shoot. I now have four (count 'em, 4) magazines, and have absolutely no intention of buying any more. Four fit in my rifle bag pockets, along with the bipod. Sure, those four are loaded all the time, but I have enough stuff to take to the range with me (rifle bag, pistol/accessories bag, ammo, targets, target stands, reactive targets, tripod, spotting scope), the LAST thing I want is another bag filled with magazines. I don't need to shoot through hundreds of rounds so fast that I can't afford to sit while I reload, and contemplate what I'm doing, what I'm shooting at, or just what a nice day it is to be outdoors (or at the local air conditioned range, depending on the temperature).
I feel the same about the 200 round drum. My objective is not to just get through the rounds as quickly as possible; it's to enjoy shooting, and hopefully do good, or maybe a bit better than last time. I'm not testing ammo. I'm enjoying the day.