Because GMO safety assessment is based on, for example in the case of FSANZ (Food Standards Australia and New Zealand):
1. So far there have been over 50 GM food applications in Australia. They have all been approved.
2. It is up to the companies that manufacture GM to research and determine the safety of their own product.
ie. the FSANZ website states:
Does FSANZ commission its own scientific studies?
‘It is the responsibility of companies that have developed GM foods to demonstrate the safety of that food and to supply FSANZ with the raw data from scientific studies to prove this…’