The advertising and the articles in the 1950s and 1960s were in large part about plinking, target shooting, varmint shooting, big game shooting, hunting of upland birds and waterfowl, skeet and trap, bench rest to some extent, handloading, and gun collecting.
You can certainly still find articles on those subjects, and there's a good deal of discussion on the various fora here. One new development is the introduction of television shows such as Guns and Ammo and American Rifleman TV and the ones on hunting.
There have been two major additions in recent years: cowboy action shooting and personal defense.
Why the latter? What changed? I think that was the question.
Well, one thing that has changed is the issuance of concealed carry permits in a lot of states, many of them heavily populated. Probably resulted in many cases from issues with crime, and much of that may have to do with an influx of drugs.
The increase in CCW, and a parallel increase in home defense concerns (you didn't see a lot of ads for home security systems fifty years ago, either), has brought about a demand for new products, which has resulted in the introduction of new guns. Hence the advertising and the articles.
That increase has brought with it an extremely important attendant need for the proper understanding of how to effectively, safely, and legally employ the new firearms, pepper sprays, flashlights, etc. Hence the articles, discussions, and shows in the subject.
My take, anyway.