My first job out of college was mostly designing hardware and writing product user manuals for our industrial I/O interfaces. I agree: those massive Omega catalogs were like textbooks to me. I learned an enormous amount about sensors and how to interface to them and that knowledge is still useful decades later.

One thing missing in this discussion is that the audience is important. Omega Sensor catalogs are great for design engineers. OTOH, you can find a lot of the same products in a McMaster-Carr catalog, but their focus is on the buyer and they are well optimized to sell to that person.