The problem is that the screen and the protector have different thermal expansion rates, and if the screen is in summer sun or sub-frreezing weather, something might crack if the entire surface is adhered, especially with curved screens. Which is why the "adhesive only at the sides" technology. Something like a Whitestone, if the adhesive remains on when it dries, is flexile, and is thick enough, prevents that. (Assuming that both the screen and the protector were perfectly annealed during manufacture - which sometimes doesn't happen, hence the "the phone was lying on a table and the screen cracked" complaints we've seen.) Curved screens are one of those "cute idea, but" things.