One thing is stronger guarantees for the receiver, who can verify that the smart contract will automatically transfer the funds. Another is interoperability. The receiver can write a contract to e.g. always donate half of that income to a charity as soon as it is received every two hours. Another is transparency and verifiability, anyone can check that the receiver is giving half this income to charity.

Not trying to get pulled into any arguments about whether cryptocurrency is good or bad, just some potential answers to your question.