Interesting question and thread, Erica. You already have some good response, but I thought I would join in just for fun.
When i was a boy scout in California, out troop, #257, often went on long mountain hikes in the hot sun. Our scoutmasters always distributed daily salt tablets. When I started going on my own backpacking trips, I never again worried about salt depletion, even on long hikes with a heavy pack.
I moved to Vancouver in 1975, and met Kathleen in 1976. We enjoyed long backpacking trips until we became canoeists in 1987. We have never even thought about taking any supplies specific to counteracting any potential salt depletion. We do, though, on our canoe trips, as others have mentioned, take a daily baggy each of our own gorp, which contains a variety of ingredients, including mixed nuts, which are salty and very tasty. In our kitchen bucket, we also have small salt and pepper shakers, although i normally don’t use very much salt. I don’t think Kathleen and I are generally working extremely hard for extended periods, or sweating profusely, on our canoe trips. I certainly might be medically naive or ill-informed, but after nearly 60 years of not worrying about salt, I won’t start worrying now. Besides, I likely have only one planned two-week canoe trip left, out on the Barrens, and it will be leisurely. Not even any portages.