So it's velcro in the back (so it can be separated to put it on), and the front inside is held snug by elastic strips. However the elastic transfers the stress of clamshelling the armor to the elastic instead of putting it on the armor. If you glue the front, the stress may cause cracks.
To emphasize: the only thing holding the front together are glued elastic strips (with E6000). They hold snug and you can't tell it's not glued.