May be, but I also don't use any projects that have you searching chat logs (even if they exist) for future roadmap information, for example.
I think the point of log history search is fair but overrated.
It's easy to point out the feature, but I'm not convinced that regular chat search is part of anybody's centerpiece day-to-day bug-hunting strategy even on platforms with chat history.
Also, some things are better off on the forum. For example, Elm has a Slack and a forum. If you need to assume that all project discussion happens on Slack to find weaknesses in Slack, then I don't find those very compelling. It's just forum vs chatroom discussion and of course there are differences, just like how chat history doesn't make a chatroom competitive with a forum.
I know it looks like I'm going out of my way to "defend Slack" in the comments section here, but I think that Slack vs IRC arguments are the perfect example of how many developers are clueless about UX and things the end-user cares about. I just responded someone who couldn't think of a single reason someone would use Slack beyond "hipsterism" whatever that means (btw, I thought hipsters liked old stuff like vinyl records and Polaroids). It's something I see as a big problem in our field along with the stereotype of how developers cannot design products (not just visually) -- these arguments tends to validate those stereotypes.