Can someone explain to me why you would want a smart contract for multi-sig? This is a feature that can be implemented easily off-chain, i.e. using split keys (

Can someone explain to me why you would want a smart contract for multi-sig? This is a feature that can be implemented easily off-chain, i.e. using split keys (Bitcoin has had this approach for some time). Seems like having this complex logic on-chain is asking for it to be exploited.