Hi Aikon,
the labels are displayed only on the metadata document. However the properties are described by their names not by the labels. Labels are useful for consumer applications, where they would like to have field labels like 'Material Number' not 'MATNR'. Now it is the responsibility of the application to display the label for the property, which is not very difficult.
In response you always get the ARRTIBUTE/PROPERTY name not the labels, labels are only available in metadata for the service.
Regards,
Atanu