you do touch L1, but only to get on and off, it only needs to happen to a coin once, and not everyone has to do it to maintain sovereignty. a person could transfer a million coins to a rollup, send them to other people who have never touched L1 before, and all the recipients would actually own them. this isn't possible with lightning. rollups don't use payment channels, they don't have concepts like inbound liquidity, and they don't require an individual user to interact with L1 to start owning his own coins. with lightning, you have to open your own channels from time to time and do L1 transactions to top off your inbound liquidity. there are also other limitations with payment channels that don't apply to rollups, such as routing issues and the size of payments.