Too Long; Didn't Read
Smart contracts have evolved into being more than just basic contracts. Now we have whole ecosystems powered by Smart Contracts! No matter how careful we are or how well tested our code is, if we are creating a complex system, there is a good chance that we will need to update the logic to patch a bug, fix an exploit or add a necessary missing feature. Sometimes, we may even need to upgrade our smart contracts due to changes in EVM or newly found vulnerabilities.