Okay, if the cell's cytoplasm has a net ionization charge of -1 (efflux of 3 Na+; influx of 2 K+), then why doesn't it just do a net efflux of a positively charged ion to maintain it for sake of osmotic balance? Well hm, it needs to efflux those ions SOMEHOW, But there aren't a lot of reactions producing Na+ as a waste product - where does the cell get all its Na+ from? (the Na+ that it wants to efflux out of the cell). Yes it is a deliberate way to maintain SOME gradient in a way such that Na+ atoms naturally influx into the cell (and drag glucose atoms along with them). But can't the same thing be done if the cell has way too many K+ ions relative to the bloodstream? (in which case some other ion, like a Cl- ion, might get attracted).