Why can draft texts not be released to the public, or at least to representatives of affected industries, or at the very least to members of parliament?

From http://www.michaelgeist.ca/content/view/4549/408/
"It is important to emphatically state that this is simply not the case for many multilateral agreements and the activities of international organizations that typically serve as the forum for global agreement discussions. U.S. NGO groups have made a strong case for how ACTA's lack of transparency is out-of-step with many other global norm setting exercises. With regard to international fora, they note that the WTO, WIPO, WHO, UNCITRAL, UNIDROIT, UNCTAD, OECD, Hague Conference on Private International Law, and an assortment of other conventions have all been far more open than ACTA. For example, it notes that the WIPO Internet treaties, which offer the closest substantive parallel to the ACTA Internet provisions, were by comparison very transparent:
The two WIPO Internet Treaties (WCT and WPPT) were negotiated in a completely open meeting at the Geneva Convention Center. The public was allowed to attend without accreditation. The draft texts for the WCT and the WPPT were public, and the U.S. government requested comments on the draft texts, which were available, among other places, from the U.S. Copyright Office."