Well it is useful at primary school when kids don't have phones. If they miss one day of school or didn't record correctly an information from the teacher parents can ask others about homework tasks, missed lessons, etc.

Also the parents delegate can relay useful info from the teacher's as the only one who has direct immediate (without taking an appointment) through that channel. State is maintaining an app/website where teachers can send messages to parents but while some do it correctly, other teachers ignore it completely.

It is also interesting when some parents find out they have an issue with a specific teacher. Like this year one of my daughter had one lazy one and parents expressed their concerns to the delegate and debated on a common message to send to school.