If diarrhea hit in an emergency situation, I want to be able to grab something, add water, and drink. Don't want to have to make up a remedy then, wasting time - just mix and drink.
Also have anti-diarrheal pills but that doesn't replace electrolytes so would keep drinking the powder/water mix after taking the pill(s). Plus, the diarrhea is due to something and if that is bacterial, don't want to stop the bad stuff getting out. If the diarrhea persists for a long time, then, of course, use the pills. What I'm saying, is, don't use the pills too quickly after diarrhea starts but do drink the electrolyte mix.
For those on a budget, electrolytes can be found dirt cheap in the feed store. Since it is geared for a 1500 pound horse, a pinch in a gallon of water will do.