Thats because everyone knows that these protectors are meant to be used in conjucntion with a bumper or case. They do not cover edge to edge in either direction.
Without the gap, you case would cause the protector to bubble at the edges.
That's not true. The SGP Oleo that I ordered directly from SGP fit the iPhone 4 screen exactly. As a matter of fact, SGP recommends using scotch tape to remove the screen protector because there is no gap to assist in removing the protector.
I think the op either received th wrong model for his phone or his order wasn't the original from SGP, most likely a knock-off.