smbclient is an optional component just providing some minor additional information about the remote SMB server. It doesn’t add any additional value to vulnerability scanning (the provided info isn’t used by other VTs) and is also not required for authenticated scans.
If your authenticated scans are failing its more likely that the target doesn’t provide all requirements for such authenticated scans. To debug your issue and to verify the requirements of the remote target have a look at the following thread and the linked documentation within it.