This isn't _as_ short-sighted as the famous "Dropbox comment"[1], but it's pretty close.
a) Slack _clearly_ offers a lot of meaningful functionality over-and-above IRC channels. "Searching" - and, implicitly, persistence - is so fundamental to the offering that it's (apocryphally) part of the acronymic name. Threading, bot support, and channel discovery are all useful features. Sure, all of those things _can_ be implemented on an IRC server, but they're not out-of-the-box.
b) Setting up and supporting an IRC server is non-trivial for a non-technical person. Sure, it's easy to you and me - but any system that can allow customers to get access to that functionality _without_ needing a dedicated I.T. team is going to be more attractive to decision-makers.
Sadly, Slack is also missing a whole lot of IRC functionality - starting with a proper desktop client. The logging it provides is a joke, even when you actually pay for it. Its search capabilities are nowhere near grep(1).
> Its search capabilities are nowhere near grep(1).
This is again missing the point. Yes, the statement "Slack's search isn't as powerful as grep's" is true - but many of the prospective users of Slack (and, crucially - most of those who make the decisions about corporate IT) are incapable or unwilling to use grep _anyway_. You are judging a tool by how well it suits your needs, without realizing that you are not its only target audience.
I think you're both missing the point, though. And it surprises me how many people miss this point even on this incredibly smart forum. The idea doesn't matter as much as the execution. The business side matters as much or more than the technology side.
a) Slack _clearly_ offers a lot of meaningful functionality over-and-above IRC channels. "Searching" - and, implicitly, persistence - is so fundamental to the offering that it's (apocryphally) part of the acronymic name. Threading, bot support, and channel discovery are all useful features. Sure, all of those things _can_ be implemented on an IRC server, but they're not out-of-the-box.
b) Setting up and supporting an IRC server is non-trivial for a non-technical person. Sure, it's easy to you and me - but any system that can allow customers to get access to that functionality _without_ needing a dedicated I.T. team is going to be more attractive to decision-makers.
[1] https://news.ycombinator.com/item?id=8863