In contrast with items, which have their tags copied from templates, host tags are only set manually or from prototypes. This limit usefulness of host tags for filtering. For instance, I cannot list all hosts with target:mysql in the host configuration or set such filter in widgets, even though the hosts have appropriate templates with target:mysql.

Zabbix could copy host tags from templates with special flag that would allow to display such tags as inherited (as in items) but not copy these tags to items that come from templates.