You are missing the "network" part of lightning network. A "payment channel" only allows unlimited "transactions" between 2 people, the "lightning network" all

You are missing the "network" part of lightning network. A "payment channel" only allows unlimited "transactions" between 2 people, the "lightning network" allows you to chain those together similar to an IP network where you can transact with anyone that has a route to you through anyone else. So if I have a channel open with my friend, who has a channel open with coinbase, who has a channel open with gemini, who has a channel open with you, we can transact over LN without opening or closing a channel.