There is also the issue with the salt by itself in desalinisation. If it's removed with water, you have to deal with that stuff. Table salt is really cheap and there is plenty of offer,, so you can't really economically clean it enough and package it for human consumption or industrial use. So what usually happens is that they dump it back at one moment or another. And that is a hard pollution, and can lead to dead zones around the desalinisation plants if not managed well enough. Being able to add it in a high demand product such as batteries takes all those hurdles away