In the US it's not legal to make hard seltzer that way. It has to be fermented. In a bar..yes.. but not as a product. In Canada you can just throw some spirits and water together.
I think there is a new young generation that hasn't had a chance to appreciate good beer and can't afford it yet. They would rather drink hard seltzer than their Dad's Bud.
I have a 6% Hard Kombucha I'm drinking right now that is a nice treat. It certainly doesn't fill me up like a 6% IPA