Can anyone explain to me why you would ever want to do this instead of proper public key encryption? A huge advantage of public key encryption is that it doesn’

Can anyone explain to me why you would ever want to do this instead of proper public key encryption? A huge advantage of public key encryption is that it doesn’t rely upon having well synchronized clocks like many 2FA solutions. Also, you can easily insert a “something you know” by putting a password on your private key.