The battery life could be a hundred hours, it doesn't matter. The fact is, you're paying $300 for a console, the same as two competitors who have considerably more power under the hood. Both competitors allow you to simply hook up their controllers via USB to charge whenever you'd care to because it doesn't cost them more than two to three bucks to throw the connector into anything. Nintendo includes the JoyCon grip with the expectation that we'll use it to play our games on. Instead of doing like both of their competitors, they do NOT soak up the teeny cost of throwing a USB connector into the grip because hey, you're buying a premium product already. No, Nintendo wants you to spend THIRTY DOLLARS to buy a grip that can't cost more than ten to manufacture, just so you can have a connector on the grip.
It is, purely and simply, insulting. They could eat this cost easy. Instead, not only are they not eating it, but they're turning around and trying to bilk me for more. And they want to do this when the market is already unfriendly to consoles as-is? It's the very definition of a stupid move.