The film that was shot couldn't simply be overscanned to 14:9 or 16:9. It would work in some scenes, but in others there were bits of the set/booms/etc visible almost upto the actual frame that was cut out. The only way to convert is therefore
Agreed. Of course, there have been more than a few remasters that didn't bother to concern themselves with such trivialities. The Buffy the Vampire Slayer remaster is an example of how you can thoroughly botch framing[0] when converting between aspect ratios. At that point, you might as well see what else you can screw up as well. At the opposite end of the spectrum, David Simon wrote a really interesting--and even-handed--blog post[1] about HBO's remaster of The Wire that converted to 16:9. He points out examples of scenes that work out better in 16:9 and those that...don't. Even when the conversion is made in conjunction with the original filmmakers, it's still a different version of what was originally intended and necessarily involves compromises.
Showing vampires in broad daylight without catching fire, for one thing. (Not applying blue filter to simulate moonlight, for shots taken in daylight but which were supposed to be at night.)
1) Throw the top/bottom parts of the frame away
2) Stretch the frame
Neither is acceptable.