Probably it is an answer. People gravitate to a distro offering them docs in their preferred style. And some of these people contribute to docs later in their p

Probably it is an answer. People gravitate to a distro offering them docs in their preferred style. And some of these people contribute to docs later in their preferred style. This process becomes self-enforcing at some point: the style is refined, the knowledge base grows, the community matures... It doesn't happen overnight, so it didn't happened in 90s. And one more reason for a late arrival: in 90s there were less people on Linux, they were not able to create all kinds of knowledge bases, so they resorted to a more achievable project of creating HOWTOs, which was meant to be good enough for everyone.