Full bleed pages started to become possible in the early 1980s, initially just on more expensive titles, because the presses that were needed to produce them were themselves more expensive to run on. But in theory, it was always possible to do Full Bleed pages, it was simply that added expense that prevented publishers from wanting to do it. Once the Direct Market opened up, and there was an interest in more niche material and in higher formats, those restrictions loosened up. Full Bleed pages were one of the things you could point to as why a certain book was in a higher format.