Roffa:
I think the point about the LL CTR might not be its size but its shape. If its boundaries or the corners of it were aligned to ground features which were easily indentifiable from the air rather than a generic CTR shape as it is now, then it might be easier for pilots, GPS equipped or not, to find those points.
Ever tried spotting the NE corner from the air? I used to fly in there regularly on traffic spotting flights and even then it was challenging to spot the exact corner if you were awaiting clearance in.