Better visibility on search engines meant more users landing on your website's content. More users landing on the website meant more revenue.
That discipline later evolved to also offer a paid option for getting users into your sites -- now considered one of the primary money makers for search engines.
15 years after, people still use search, true -- but not as much as they used to, and in my opinion, will barely do so in the future.
Why? People have no idea what they want to do next, so how can they search for it?
The world is transforming from actively pursuing to passively discovering. People might search for an article or a video, but then discovery vehicles will get the user to bounce from one piece of content to another. In fact, I'm not even sure that search will remain to be the anchor as it is today for people to land on the first article or video. As an example -- social channels are already getting massive momentum and users are spending more time on them (Facebook versus Google)
The biggest asset on the Web, in my opinion, is "owning" where users go. Today it's primarily Google through its search engine -- a very lucrative business indeed. In the not-so-far future, I think that discovery tools -- from social vehicles to recommendation engines spread all around the web content pages, offering people content they might like from the Web -- will win.
If that's true, the huge market of optimizing search and paying for it (SEO/SEM) will slowly transform into optimizing and paying for Discovery tools that own users' attention and help navigate them to the "best next thing."
I would call it discovery engine optimization (DEO).