I've sometimes suspected it's an investment thing. A Discord server or subreddit is free, can be setup or abandoned at any time, and (on Reddit) can be taken over by the site or another team whenever you move on.

So, there's a not much of a reason to care how badly you're running the place. You didn't put any time or effort into its setup, and you're not losing money if the community dies out.

Meanwhile a standalone forum costs money to host, and it feels bad to pay $X per month for a ghost town. So, there's at least some level of interest in keeping it running smoothly and fixing issues, since otherwise you're wasting your time and money.

Alternatively, having to pay might just mean the average forum owner is an adult with real world experience rather than a kid or teen or internet shut in that's running the community for laugh/sees it as a quick way to get power over people.

The generation before that (yours truly) still remembers the usenet glory days, and the liberal use of the kill file [1].

[1] https://www.catb.org/jargon/html/K/kill-file.html

It notably lacked up/downvoting which is a cancer foisted upon open discussion.

Discussions ran chronologically as they would in real life.

Imagine having a remote control you could point at people to increase and decrease their speaking volume. That's what voting is.