Because the account is code, it can enforce rules: daily limits, allowlisted recipients, social recovery through trusted parties, session keys for a single app, and paying fees in a token instead of the native coin. account-abstraction standards made these mainstream.
The tradeoff is that you now depend on contract code being correct. A bug in the wallet contract is a loss vector that a plain key pair simply does not have, and upgradeable wallets carry admin-key-risk.
Deployment also costs gas on each chain you use, and behaviour can vary across chains, so test with a small amount on each network before relying on it.
Related: multisig-wallet