Why is necessary for an export firm to go in for pre-shipment inspection?

It is necessary for an export firm to go in for pre-shipment inspection because pre-shipment inspection report is required to be submitted along with other documents at the time of export. Such an inspection is not compulsory in case the goods are being exported by star trading houses, trading houses, export houses, industrial units set up in export processing zones/special economic zones (EPZs/SEZs) and 100 percent export-oriented units (EOUs).