Because doing so would ignore the benefits they provide. The reasons we started using them over the alternatives. Their effects are reasonably well understood, enough to use them in a likely safe manner. The EU experiment (the ban) will provide another data point to inform the cost-benefit calculus.

Relying on complete knowledge of somethings effects before use is impractical. Do you know for certain that goat milk doesn't cause Alzheimer's? No? That doesn't mean we ban its production until it is better understood. Yes, this example is a a bad one, not exactly analogous, but only because I didn't take the time to think up something better. I think the point is clear enough.