Jeremiah,
This is my thoughts. First, speacking from an American Catholic, I think part of the answer to your question lies in the American psyche. We as a people are not very interested in history as are some other cultures. I think many would agreee with me that in the American mind, the past (history) is all well an good, especially the more interesting parts for the individual, but we as a people seem to always be looking forward,“what will tomorrow bring…” (or as the joke about New Yorkers is, “What have you done for me tomorrow?”). So it is just part of our culture (or may I be as bold as saying ‘nature’) as Americans to too often look to the future and forget the importance of the past. (Try teaching history - American or any type of history to high schoolers for a semester and you will understand what I mean)>
The second reason that comes to my mind is the Church for most Catholics just has always been there and too often we forget to question why. This may sound like my first point, however, here I would like to add a slight difference. The Church is like a persons family. We all know something about our parents and grandparents, but it is almost as if we take our family’s history for granted and really do not dwell on it (maybe this does tie into my first point closer than I realize?). As a result, like many a family’s fokelore we just accept what we are taught or better what has been handed on to us with out any real desire of dwelling into things any deeper. For example, in my past experience, most people I talked to understood the Peter was the “First” Bishop of Rome, but were very surprized to find out that there was already a Church, perhaps several, in Rome by the time Peter arrived there. Or that the Church at Antioch was the first place we were called “Christians” and that there were Christians there as a community before any apostles had arrived.
Most just though the Church at Rome was established by Peter and set up by him just as we have it now.
Why they thought this way, again maybe its be cause we are Americans and that the Church always being here, just like our families are, the thought never really occurs to most to dwell any deeper.