I agree with Matt. Security wise it doesn't make a lot of sense.
But
it protects the casual user from shooting himself in the foot. What's
the downside?
It often feels similar to the alias definitions of "rm" to make sure
Unix admins don't accidentally remove a file.
Then again no real downside...
From a security standpoint, leaving the root account also open
for ssh logins, is that a real problem. Otherwise why not leave
root and some pseudo-user account open and let the user decide
which one to use?
best regards,
Florian La Roche