I'm guessing that several of those reasons are valid, at least in part. But I think that it's more likely that the main reason was because he thought it was worthwhile to guarantee that the memories of all of those young people would be kept alive and that anyone who might be interested in looking for this boy or that girl would be rewarded for their efforts.
Recently, I completed a project of similar length and complication that might also seem overdone to some folks. In 2009 I discovered a couple of shoeboxes filled with correspondence between my parents during the 18 months of courtship just prior to their marriage in 1950. During that time they graduated from St. Olaf College, my Mom taught school in Spirit Lake, Iowa and my Dad graduated from seminary. Their letters detailed not only the strong feelings that they had for each other, but the many arrangements that were necessary to allow them to meet each other as often as possible given the geographic challenges of their frequent separations.
I decided to prepare a book of their letters so that I could make copies and share them with family and friends. (Don't be alarmed: I removed a couple of letters that I felt were too intimate to publish. The rest are quite tame and often extremely funny.) I read all 150 letters three times and spent hours at a copier reproducing the letters and envelopes to get them ready to present to a printer for publication. The finished product was a smashing success in my opinion and my family responded favorably as well. My only disappointment was that there were two periods when I had just one side of the conversation. The answering letters from the other party were missing. At any rate, I felt a deep satisfaction at having assured the survival of these priceless exchanges between my parents for the benefit and enjoyment of their descendants.
Norhian scans. Do yourself a favor and check it out. Oh yeah, and surprising personal postscript: last week I found my partents' missing letters! Not sure what, if anything, I'm going to do about it. Probably just read and enjoy them.