If I understand how this pillarbox works?

Quote The pillarbox (window box) is done to retain the original 4:3
aspect ratio of old filmed and videotaped material (some early sound
films like Charlie Chaplin's "City Lights" and arcade video games were
in narrower screen sizes and have to undergo this reverse-letterbox
format to be displayed properly on modern TVs). Quote

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So it was a widescreen filmed with black lines on top and bottom for
a 4:3 TV .But using this widescreen filmed black lines on top and
bottom for a 4:3 TV on a 16:9 TV you get black bars top and bottom
and right and left.

Why not just get the same program 16:9 widescreen than trying to use a
4:3 widescreen where they have to put black lines on top and bottom
to show widescreen on a 4:3 TV.