seems that how they generate the keys, it's basically the same. The same password would generate the same keys. Anyone who uses the same password would be able to decrypt data sent to anyone else using the same password.
If I send you an encrypted file with minilock, you won't know my password, and I won't know yours, but you'll be the only one that can read it, and also you'll be sure I've sent it and not anyone else.
Bob sends public key to Alice. Alice uses public key to encrypt file and sends to Bob. ONLY Bob can decrypt the file (using his PRIVATE key).
If you sent a password, then anyone who intercepted it AND the encrypted archive would be able to decrypt it.