What's not digitized in Proquest (might be an ongoing series)

I learned yesterday that letters to the editor to the Philadelphia Jewish Exponent in 1996 (and perhaps other years) are not digitized in ProQuest and nowhere in the metadata (as far as I can see) is this noted. How do I know? well, I was trying to remember a letter to the editor that I published pointing out that saying the Israeli electorate was not split on Netanyahu (in the 1996 election) because he had a 10-point margin among Jews undermined the claim of Israel as a democracy. I remembered a response saying "Shear is hung up on democracy" (or the like). So I went searching for this in proquest.... nada. I found my clippings of the letters (mine and the response) in a file folder after some searching through old files boxes. Here is my letter:

And the response. Apparently I am “hung up on the word ‘democracy.’”

But forget my political hangups. What I really came for was to point out this lack of digitization of letters to the editor & the implications for historical research. This seems deeply problematic given that there is no way to "turn every page" here as Robert Caro suggests.