How is slack deep in a company's workflow? In other words, what stops them from switching to an alternative chat?

Internet access is deep in company workflows as well, but that doesn't mean they can't change ISPs.

Are companies building their ordering systems to depend on slack API's or something?

>Given how deep it is in a company's workflow you could think of it almost like an operating system where apps can attach to

Off the top of my head, both mattermost and rocketchat provide compatible webhook apis that make them drop-in replacements for slack.

So not that deep into peoples workflow...