Because the previous generation could only publicly shame through the press, and the press was reluctant to print potentially libelous attacks.
Public shaming as an immediate reaction is fairly recent in the short history of the internet. The technology supported it easily in the 90s (or even late 80s using newsgroups), but it didn't become a common practice right away. Retweeting and hashtags seem to have turbocharged public shaming.
The social norms of my generation (49 yo, in California) required that one try to settle business disputes directly between the parties before resorting to public shaming. I still abide by that norm, even though I recognize that many people think differently. Which way is ultimately better for society isn't clear yet.