I recently found the late Arthur Bergeron's Guide to Louisiana Confederate Military Units, 1861-1865, on my own shelf. Not sure why I did not look at it when I made my initial post a few weeks back. Crute's Units of the Confederate States Army lists 77 infantry, cavalry, and artillery organizations from Louisiana. Bergeron lists 111. So, the new number of Confederate regiments, battalions, and batteries raised during the war stands at 1,500. I image this number will continue to rise.
A couple of days ago, I received this question through my contact form, from Edgar: "I found many union regimental histories/biographies on the Hathi Digital website when I was researching Sherman's march campsites (Goldsboro-Raleigh) last winter, but I can't find much about Confed. regiments there." So, why not more Confederate regimentals? That's a question. The reason that a person cannot find more Confederate regimentals on online databases like HathiTrust is probably because they were not written.
Using North Carolina as a guide, we find in Stewart Sifakis's Compendium 233 Confederate regiments, battalions, and batteries. Of those 233 organizations, only seven had histories written and published by the veterans themselves. Those seven are:
Harris, Historical Sketches of the Seventh Regiment North Carolina Troops, 1861-1865 (1893)
Smith, The Anson Guards: Company C, Fourteenth Regiment North Carolina Volunteers 1861-1865 (1914)
Mills, History of the 16th North Carolina Regiment in the Civil War (1901)
Carr, History of Company E, 20th N. C. Regiment 1861-1865: Confederate Grays. (1905)
Underwood, The 26th Regiment N.C. Troops, Pettigrew's Brigade, Heth's Division, Hill's Corps, A. N. V. 1861-1865 (1901)
Sloan, Reminiscences of the Guilford Grays, Co. B 27th N. C. Regiment (1883)
Day, A True History of Company I, 49th Regiment North Carolina Troops (1893)
If my math is right, that is only 3 percent of North Carolina regiments, battalions, and batteries that had a book written about their service prior to the 1960s. To take this a step further, of the seven, only three are actually regimental histories. The others deal with companies. Now, to North Carolina's credit, the North Carolina Confederate Veterans Association, under the direction of Walter Clark, began to collect essays by veterans about their regiments at the turn of the 20th century. This was later published in 1901 in a five-volume set. To my knowledge, no other state has anything equal to this: a short history of almost every regiment, written by a veteran of that regiment. (By the way, all five of these volumes have been digitized and are online.)
So to answer the question posed, the reason there is not more information on these regiments is because the veterans did not write down their histories. Union regimentals are plentiful. Confederates, not so much.