Why do customers ask to meet the manager in case of complaints?

In most of the cases they think that they will get a instant resolution from the managers as the subordinates don't have the complete authority to take decisions.

But in case if the customer is getting proper & positive response from the subordinate employee, then they are doing a great job where there is no need of approaching the manager. 

The word 'manager' says it all. He is the one respinsible for all activities in the company.

Managers are there for;

Organising

Monitoring

Managing

Executing 

Directing

Solving all company related activities..