In IRC, anything that happens while you don't have an active session just doesn't exist.
That might work for some communities, like programming language groups where I can hop in, talk about something with whoever's online, and hop back off.
But if I'm chatting with my friends and we're trying to make plans for the weekend, everyone really needs to see that conversation regardless of whether they have the client running right this second.
Other chat protocols fix this but lack the base, and are having trouble competing against the likes of Slack or iMessage in different use cases for example.
I'm excited to see how Purism's Librem 5 is going to play out with matrix as it's primary communications platform.
This is exactly why people who are pro-IRC are watching the sun set on IRC and they don't have a flaming clue why beyond condescending suspicions like "it's the users who are idiots."
Sometimes I wish I didn't have so many messages saved forever tho, honestly.