This would give users a false sense of security. It would offer very little protection against viruses or hackers who know what they are doing.
Then how come every competent person uses passphrases for their SSH keys and GPG keys and considers it a good thing? I guess we should remove the feature from those programs because it provides a false sense of security?
Competent people already encrypt their savings wallet with something like Truecrypt. This isn't too hard to do. So I am assuming this feature is aimed primarily at non-technical users.
It's not a bad thing to this include feature in the client, as long as you make it clear to non-technical users that the feature by itself will not protect them against thief viruses, and that additional measures are required.