Imagine if you couldn't receive e-mail while you were offline!
This isn't to disparage IRC and friends too much, obviously there's huge value in it existing as a synchronous chat room. Just... async chat is a thing that totally happens for most people.
this value sell shifts in the mind of the non-technical person once they're told that the feature they want implies non-ephemeral data that will be systematically sifted through either for legal or financial benefit by a third party.
in other words : the reason why 'async chat is a thing that totally happens for most people.' is because a vast majority of people are simply unqualified to even see the problem, much less seek alternatives or solutions to the data hoarding that they must comply with.
this creates a social effect and pulls everyone into Discord, regardless of their beliefs on the matter, simply because it has become 'the only game in town'.
regardless of personal preference, centralization of these kind of things is BAD for the user in nearly all circumstances aside from convenience.
That you can, with augmentation and diligent op-sec, get something a bit better than Discord isn't a great selling point unless you have the time and resources and buy-in already, not just for yourself but from everyone in your group. At which point, there are still better options than IRC.
For decades now, the main draw of IRC has remained a fetish for conspicuous configuration, as it embodies a sort of brutalist architecture of communication software. The excuses change every few years, but the love for cobbling together a barely workable system from parts remains core.