Because internationally, every single organic certification system prohibits the use of GMOs in their production system. You can't get fertilizer drift, and in terms of pesticide and herbicide use, organic producers have a buffer that they need to be responsible for on their land. They also need to provide affidavits from their neighbours, who are acknowledging that they're running their farms organically and that they have agreement from their neighbours not to spray during wind, and so on and so forth.
It's much easier to take steps to protect the organic integrity outside of the GM issues on farm. What happens is because—