Use case example (one of many):

You have 2 node patroni cluster in Amazon, Load Balancer (for some reason patroni API status was ignored by LB itself) failed to switchover and Server generates tons of logs with read only error, because LB points to read-only database. Technically connection is not lost and administrator will not receive "database down message".

Or accidentally DBA changed with Read Only permissions account for Zabbix Server.

This will help avoid situation with no events/problems from Zabbix and not working Zabbix.