Rainbow tables are only useful in certain circumstances, namely when the password to something is hashed and stored somewhere that is accessible to the person wishing to find your password. Proper security measures prevent anyone from gaining access to the hashed password. If they have the access needed to gain the hash of the password, why would they really need to crack it? They already have access to the data.

For encrypted data, they would be useless, as proper encryption software wouldn't need to store a password. For web passwords, if they don't have access to the server where the passwords are stored, rainbow tables would again be useless.

Just to add something: Nearly all real life methods of gaining a persons password revolve around some workaround, mainly because trying every single password is so time consuming. IMO, bringing things up like that in a discussion of password complexity tends to be counter-productive because it makes people think there is no point in a complex password if it can still be cracked so quickly.