It's the only way Bitcoin can scale to major-currency levels, since every on-chain transaction is seen by every full peer.
If you have a bunch of "banks" who provide checking accounts, they can use on-chain transactions just for periodic settlements. "In the past day you sent me checks worth 10,000 bitcoins, and I sent you checks worth 11,000 million bitcoins, so now I'm sending you 1000 bitcoins."
If you have a bunch of "banks" who provide checking accounts, they can use on-chain transactions just for periodic settlements. "In the past day you sent me checks worth 10,000 bitcoins, and I sent you checks worth 11,000 million bitcoins, so now I'm sending you 1000 bitcoins."