These classic titles are 4:3 films, but they are
encoded as 16:9 in the HD resolution (either
1920x1080 or 1280x720) coded video bitstream.
The black sidebars are part of the 16:9 image.
When you instruct the player that you have a 4:3
display attached, it dutifully letterboxes the 16:9
image to create a properly dimensioned display.
The player has no way to know that there were
black sidebars in the image. For these 4:3 films,
the result is dimensionally correct, but does not fill
the 4:3 display's screen (it's "postage stamped").
There are a couple of ways to handle this issue:
1) Some sort of AFD like metadata. That is, something
that can instruct the player that it's 4:3 content in a
16:9 raster.
2) A true 4:3 HD format such as 1440x1080 (with the
aspect ratio set to 4:3, not 16:9).
Solution #2 (1440x1080 with 4:3 aspect ratio) was
actually included in early versions of the HD-DVD
specification. It did not make it into the final
specification, most likely because there's little
or no encoding equipment that can create a
1440x1080 4:3 aspect ratio bitstream when
fed a 1920x1080 16:9 raster.
Solution #1 is a lot of added complexity to solve
a point problem. 99 and 44/100 percent of Blu-Ray
enthusiasts have a 16:9 display. To quote Mr. Spock,
"Were I to invoke logic, however, logic clearly dictates
that the needs of the many outweigh the needs of the few."
