That would be ideal but given how we keep slipping our climate goals, I think it’s worthwhile to have contingency plans to provide some societal stability. If you think we’re not devoting enough resources to combatting climate change, just wait till nations are focusing on fighting water wars and puting down riots. Having ways to provide people with clean water where they live (i.e. most, not near glaciers) isn’t just humane, it helps prevent environmental damage. Wars and their incredible destruction aside, we’re currently draining aquifers and rivers dry all over the place.

Edit: also, if it does become a problem, removing the salt from seawater is easier than removing the water from seawater.