Yeah, what you just said is probably the case for the majority of Slack's users, and I get that.
My perspective is framed by working with an EMS provider (PCB design & assembly) who does business in some highly regulated fields. We've started using Slack in the last couple months for some of our teams, and love it, but the idea of using it as a catch all strikes me as questionable.
If we used Slack for actually talking about the design/assembly portion of the business, and not just coordinating sales and marketing efforts, our customers would flip shit. And rightfully so.