In years past when I lived in libraries (not literally), I spent huge amounts of time doing research. One of the most useful tools was to read the card catalog. To do this, you needed the skill of flipping through the cards very fast and also being able to read the information in the split second the card was visible. The advantage of this type of research was an overview of the target subject, with the result that I often found valuable books or records I didn't know existed. Cataloging books for libraries was partly science but mostly art. The cataloger had to know what the book was about and decide about the assignment of categories. Since the cataloger had a different perspective on the information in the book or document than you did, you got a bonus look at the information. At least two people's opinion about what might be in the book.
There is an old adage that you can't tell a book by its cover and it is so true. Even though you couldn't tell much about a book by its card in the catalog, you did have a chance to see that the book was categorized in the same way as other similar books. After finding an interesting entry in the card catalog, you could then go to the shelf and read the shelves to see what might turn up of interest.
Now that is all gone. When I go to the Family History Library in Salt Lake City (or any other library for that matter) I can no longer browse through interesting related entries in the card catalog. If I want to see related subjects, I am left with reading the shelves. The main problem is that if an item is mis-shelved or checked out, then I miss it entirely. Because of the Dewey Decimal System of book cataloging, books with similar topics were shelved together. In today's electronic catalogs, there is no physical counterpart to the catalog entries. The computer catalogs are very efficient in finding books with similar words, but leave out physical proximity entirely.
Let me give an example. Let's suppose I am looking for marriage records in Rhode Island. I look in the Family History Library online catalog under Rhode Island. I find topics called Vital records, Vital records - Indexes, and finally, Vital records- Inventories, register, catalogs. But guess what? Clicking on one of the entries gives me a long list of items, which are all over the library and mostly on microfilm. One of the entries, Vital records & indexes for births, deaths, and marriage, 1853 through 1900 is contained on 72 microfilm reels! Here is the problem, I now have a huge reference source but I have absolutely no insight into what other records might be available. There is no particular order to the microfilm cases and looking at adjoining films is a total waste of time, they could be an entirely different area. There is no convenient way to look at records in the same category.
So even though we have gained access to a huge number of records. We have also lost the association of those records one to another. Part of the solution to this loss, is the reference wiki. Here, people can list resources and show associations that used to exist in the paper card catalogs. But going back to the Rhode Island example, how was I to know from the online catalog that some of the most valuable records for marriages, deaths, births and other information are contained in the town records? I may never discover this, because town records are listed in another category unrelated to marriages and physically the books and microfilms are no where near each other. In the card catalog days, I would probably find a reference to marriage records and might also find the same description on a card for the town records. Sometimes much is lost when much is gained.