I think a lot of new climbers wring their hands over what to carry on the Big R because it is one of the few variables they have control over. One can also train appropriately, but one can't control the weather, objective hazards, conditions on the mountain, or their physiology and reaction to altitude. Also, taking time off from busy schedules, flying across the country, etc costs more time and money than driving from Seattle so non locals want to stack the odds in their favor as much as possible. Not to mention non locals do not have the opportunity to work out their systems on lower but similar mountains like Mt Baker.