It's always interesting to see different people's interpretation of things relating to diet and nutrition, including water intake.
I'd like to add that most people consume way too much salt, in the form of salt added to what they are cooking, and in terms of salt contained in processed packaged foods, and in restaurant food, etc. Sure, sodium and chloride ions are essential nutrients, but added salt – i.e. crystal form of sodium chloride – is a food additive, not a nutrient. I make this distinction because of two reasons: 1) salt in this form is highly addictive, and 2) the amount used in the food supply and "culturally" is beyond healthy amounts. Forget the FDA-approved amount of sodium per day – it's propaganda. And, if you are relying on salt for your daily minerals, you are making a mistake. It doesn't matter whether it's Morton's table salt, sea salt, Celtic sea salt, or pink Himalayan – it's all 97-99% sodium chloride crystals.
Excessive intake of salt causes a bunch of negative effects on the body. One of those is dehydration. So, I'm not surprised that doctor's recommend consuming liters of water per day. (With the ideal diet, you can get enough water from the food you are eating, but how many people have an ideal diet? It's a difficult thing to maintain.) Another effect of salt is high blood pressure. The combination of dehydration and high blood pressure can cause symptoms like: headaches, insomnia, nightmares, and stimulant-like effects (like caffeine). Both high blood pressure and dehydration are associated with many different serious negative effects on physiology.
The addictive nature of salt in the diet is so insidious that I think most people just can't overcome the addiction. They associate salt with flavor, and then it becomes a vicious cycle. I have some friends in this category, and I'm concerned about it, but... what can you say? They tend to just joke around about it, like it's no big deal. The older you get, the more of a big deal it becomes. What I recommend is to take a break from added salt, to see what it's like not to consume so much salt, but you have to be careful because A LOT OF THINGS that come in a package, container, or bottle contain added salt. If you do this test long enough, your body will come back into balance, and you'll feel a lot better. You will see just how much salt was affecting you.
A great way to cleanse the body of excess salt (and excess sugar by the way) is vigorous exercise that produces a lot of sweat. You can also balance your electrolytes by consuming high-postassium fruits, for example bananas in a smoothie.