Yes. Safe is a smart wallet with multisig capabilities built in that make it robust and secure. A user can still choose not to use multiple signer and just use one.
The Safe smart account is much larger than the Safe(wallet) interface. It is the core infrastructure used to embed smart accounts into any product. Worldcoin most notably uses it to deploy all their user wallets on the world app.
There are many reasons but the biggest one is security. Multiple signers to authenticate an account gives users the security like an onchain multi-factor authentication.
Aside from this, many advantages like transaction batching, gas efficiency and using several Safe(Apps) can be enjoyed by users.