most users know that they should not use short, weak passwords. unfortunately, without any technical restrictions in place, some users still end up with very bad passwords.
in zabbix, there currently are no password complexity requirements. some could be added, possibly with the help of https://github.com/cracklib/cracklib

it has been mentioned that an ldap backend would allow this. unfortunately, ldap is not always a possibility (no access to ldap servers from zabbix or a dedicated system that is not supposed to integrate). additionally, user management becomes complex, as new users cannot be added from zabbix alone anymore.