Doesn't have to be "on chain". The ability to use Bitcoin via on-chain, self-custodial lightning, or even via hosted lightning model is the ultimate power. It provides room for people who are skeptical about custody or who are less equipped to do so (technically and otherwise), while at the same time ensuring that anyone can choose at anytime to exit into self-custody without being resisted.

Lightning and e-cash doesn't pay (enough) for network security. Big players may even have unpublished zero-conf channels and pay nothing. The argument that on-chain fees will be so high in the future doesn't convince me. People will choose cheaper ways for payments and the network will get insecure and useless.