All my enterprise clients are MSFT shops. They will make due with whatever collaboration tools that MSFT provides. Also, they would never use a product from a company named "Slack".
Exactly. To some extent, all Microsoft has to do is make their product offering good enough to prevent folks from leaving for products like Slack or Hipchat. Skype for business allows you to send ims, files, share your screen and clumsily do group chats. It does most everything people need to do well enough and it comes pre-installed with Office.