Why are certain pre-war cards so scarce?

[tbob]

Certain color variations of cards can be very scarce with no rhyme or reason to their difficulty. My nominee is the E98 Lajoie with red background. There's been a lot of debate on the board and elsewhere as to which background color (blue, green, orange or red is the toughest) and there doesn't seem to be a real consensus. For a while, the popular argument was that the red background cards appeared less often and were presumed toughest, but arguments have also been made that the other colors are equally tough. Having collected several sets of these cards over the years, I have noticed that certain players in certain colors seem to pop up very infrequently but none more infrequently than the red Lajoie. I have a theory that one reason for their infrequency is that the E93 has the same pose and has a "reddish" background (although not the bright red background, but a muted red background) and thus has mistakenly found its way in to some E93 sets. The only E98 red Lajoie I have owned was purchased in an E93 PSA holder and when I cracked it out and submitted it to SGC, it temporarily appeared in an E93 SGC holder before the problem was finally resolved and it now appears in the correctly described holder, although sadly I no longer own the card.
Having collected many, many E94s and E98s over the years, I have never run across another card with as strange a scarcity level as the E98 red Lajoie with no seeming explanation.