From the point of view of the employer it's stupid not to put all your eggs in one basket. For $10 a month per account, you get email (unless you have thousands of accounts, this is already worth it), instant messages and a softphone solution, office tools that you needed to buy anyway, and centralized user management for it all. All alternatives involve either still contracting it out to a probably les competent team, or hosting it in house at significant cost. On top of that, the day it all crashes down and burns their business to the ground, insurance pays out because it was cretified and wasn't an in-house solution that the insurer can point at and drag you to court with.