SEO is one reason that’s less common.

No it isn’t. SEO is about faming the search engines to place their data ahead of everything whether relevant or not.

Yahoo was fantastic in it’s time because it was human curated. No SEO could bullshit a person reading the page and categorizing it.

Google was fantastic at the start because SEO couldn’t game the system. Google was famous in the early days for maintaining quality by keeping their algorithms secret and constantly changing so that SEO couldn’t break their search.

I’m speaking as someone who was first on the Internet in the 80’s.