The Titanium Powerbook had a tiny bezel, almost a third the size of the bezels on the current MacBooks so it's not a screen tech issue.
It's a human usability issue. How would you hold the full size ipad in portrait mode with one hand if it had a tiny bezel? The Mini can have a smaller bezel because its possible to hold it with one hand spanning across the back, as opposed to gripping one side. The design of smaller devices does not have to carry over to the design of larger devices, so just because a small iPad has a small bezel doesn't mean the larger iPad has to have the same bezel.
It's a human usability issue. How would you hold the full size ipad in portrait mode with one hand if it had a tiny bezel? The Mini can have a smaller bezel because its possible to hold it with one hand spanning across the back, as opposed to gripping one side. The design of smaller devices does not have to carry over to the design of larger devices, so just because a small iPad has a small bezel doesn't mean the larger iPad has to have the same bezel.