There's an issue of scale to it all, and interconnectivity. Back in '98 you could reasonably post something in one forum/BBS/IRC channel and it would only be viewed there. There was no way to look up who was on what website or room and where they regularly hung out. And even if there was, it's unlikely that more than ten people would ever see what you posted. There weren't enough people to care, and there wasn't any extrinsic incentive to look up what people did outside of your tiny island. Eventually the island would sink, and all traces of it except maybe an archived snapshot of the home page would remain.

Smartphones changed that with Youtube and Facebook. Youtube incentivized you to use a Google account, and Facebook wouldn't let you use it anonymously without an account. Because you could use one account to log into multiple places people could track you across websites. People could make archives, screenshots, and transcriptions of anything you had done with those linked accounts. With this change there was no safe corner to hide if you said something stupid. And because so many people were foolish enough to tie their real identities to these online accounts with their real names or pictures of themselves, it gave a way for particularly unruly people to track these individuals even offline. There was now a real danger if you said something stupid, because instead of just getting your post deleted or starting a derailment in the thread people could harass you at your home, get you fired, and even send the police to terrorize you in the middle of the night via SWAT raids. It's no longer just one person calling you out. It's now hundreds, maybe even thousands, all armed with information.

And this is why I say it's stupid to require phone numbers and real names to sign up for insignificant things like being able to view someone bake a duck shaped cake live over the internet.