That's by design for now, to be changed in a future release. however any profile which you install can be signed.
https://www-secure.symantec.com/connect/articles/ios-profile-security-how-sign-and-encrypt-ios-configuration-profiles
And
https://www-secure.symantec.com/connect/articles/ios-profile-security-how-sign-and-encrypt-ios-configuration-profiles-using-openssl