Due to the extremely poor infrastructure in India, couriers often find it very difficult to locate most places, especially in posh areas of the small towns. Compared to middle class and lower middle class localities, there are relatively few people roaming in the streets in posh areas, so the courier finds it difficult to get directions to any place asking people for directions.
If the courier is not familiar with the area, they usually will phone the person to whom the letter or parcel is addressed to ask for directions, However in many cases for indian citizens, their phone calls are routed through R&AW/CBI/indian intelligence employees who will often block the phone call out of hatred or malice or because they are too busy with other activities.
So the courier will try contacting the recipient of document, he will often get a message that the phone is switched off. It appears that courier companies are covering large areas and do not have detailed information about houses in most localities.