When using a single password for all sites, any malicious or breached website exposes access to all your accounts. When using a password manager, only a breach

When using a single password for all sites, any malicious or breached website exposes access to all your accounts. When using a password manager, only a breach of your computer or the password manager itself (or your email) will totally pwn you. Breaches online are very, very common, and I would expect any password used on every single website you use to get leaked quickly.