It's a wonder that any of these services enjoy success when IRC exists.
- automatic backlog resumption
- server stored pageable backlog
- continuous presence (you don't disappear from the channel when you leave, you're just marked as away)
- authentication built into the spec rather than implemented using a "services" layer
- general upgrades to what is allowed in the chat, such as long pastes, inline images, and file uploads
If you haven't tried Matrix yet (the best client is probably Riot at https://riot.im/ ), I encourage you to give it a try. It's essentially next generation IRC.