Often you want to login to the client to check only the blockchain or the voting, without executing any transaction. For this, the passphrase should not be needed. For example Nxt (using also brainwallets) has the possibility to enter (or choose from a dropdown) only the account number on the login page without entering the passphrase. This brings you into the client, allowing you to do anything that doesn't need the secret. If you want to execute a transaction, you still have the possibility to enter your passphrase.
This would also increase the security, because you don't have to enter a passphrase if you don't really need it
Often you want to login to the client to check only the blockchain or the voting, without executing any transaction. For this, the passphrase should not be needed. For example Nxt (using also brainwallets) has the possibility to enter (or choose from a dropdown) only the account number on the login page without entering the passphrase. This brings you into the client, allowing you to do anything that doesn't need the secret. If you want to execute a transaction, you still have the possibility to enter your passphrase.
This would also increase the security, because you don't have to enter a passphrase if you don't really need it