There's still some excellent documentation out there. But basically what happened is the immediate response cycle of the Internet.
You don't know what to do? Well, google it, look up Stack Overflow, open an issue or write the company/developers. You just couldn't do that when the applications were mostly offline and you didn't exactly have a full set of international call agents well versed in the software.
I also believe that more companies had tech writers, which is one of the worst fatalities that the "full stack" mindset inflicted on us. Of course, the open source part doesn't really have the option here.
And once you have this, there's a certain peer pressure. IBM delivers a whole shelf of docs for one product? Welp, need to do that, too.
There's also a definite movement towards video material, although that's not a total excuse. As others in this thread pointed out, dBase had video tutorials too (If I ever make it big enough with a "boxed" product, I'll hire some guy with werewolf hair or a woman named Cheryl to do that with a VHS aesthethic).
Videos and reference documentation doesn't go together.
I've also encountered more "code clearly and you don't need docs" than previously in recent years, maybe Uncle Bob or some other "thought leader" is preaching that again.