A shipping label is a requisite paper affixed on the package box in the shipping process. It contains very important information for a courier to ship packages. If your shipping label of an item is pasted in a wrong manner or is damaged, wrinkled, torn or etc., the shipping process may be affected and thus you may receive your item in delay or simply lost your package.
To know why that would happen, you may need to know how the sorting process works. After your package is packed by someone and was carried by a courier, it would go through a sorting machine. The barcode on the shipping label would then be scanned, if your shipping label was pasted correctly, then it would be scanned successfully and went to the right shipping process until it was delivered. But if it was not pasted correctly, it then would be sorted and checked by the human labor. This will result in two conditions. One is that it was recognized by the human labor and then entered into the right shipping process. The second is that the shipping label of an item cannot be readable by a human either, then it would be returned to the sender or abandoned.