was told that using Jello works as a good electrolyte replenisher
Hence the reason why hospitals give it to patients.
Probably not. It does have a little bit of sodium per serving (about 100 mg). More likely: it's easy to eat because it's cold and mild, and anyone (except NPO's) can eat it because it qualifies for a liquid-only or low-residue diet; since it's solid in the mouth it gives you the psychological benefits of chewing and some satiety from it taking longer to eat. It's also cheap and easy to prepare in large amounts.