Unless I'm mistaken, water poisoning is only a credible threat when you consume exclusively those high volumes of water and nothing else to raise the salinity of the water in and around your cells. Over the course of a day, most of us get (much) more than enough sodium from other sources to eliminate any risk of water poisoning from 3.8L of water per day.
Yeah -- similarly to you, I'm pretty convinced that water poisoning is only a worry if you're unwell (mentally and/or otherwise) or do unusual things like water-drinking competitions.
