Twenty years ago is a useful time frame. That was about when Twitter, Facebook, and blogs began to make their mark and authors faced a new pressure to promote themselves on social media.

But some aspects of the promotional push pre-date social media, particularly book tours, which go back more than 30 years. Writers would see other authors going on cross-country book tours, and if they weren't getting them from their publishers, might hear: You should set up your own book tour.

A fair number of authors still do hire publicists to set up at least regional tours of bookstores and events for them. Social media (and, more recently, the pandemic) did away with a lot of those, though.