A full backup of an ESXi host is not necessary because the installation of ESXi is a quick and simple process. Host configurations should be backed up in order to quickly restore the configuration of a host in case ESXi needs to be reinstalled.
If hosts are deployed using Auto Deploy or the host configurations are stored in a host profile, the individual backups of host configurations may not be necessary, but are a good way to ensure that a backup of the host configuration is available in case there is an issue with vCenter or a configured host profile.
