They're deployed on Azure and have a deep partnership with Microsoft, so they can't "simply" use a different cloud.
Also, recommending a black box managed solution isn't an option for some large companies that have their own hardware & datacenters and which may want to use open source solutions they can easily deploy, fork and support themselves to keep costs under control.
Also, recommending a black box managed solution isn't an option for some large companies that have their own hardware & datacenters and which may want to use open source solutions they can easily deploy, fork and support themselves to keep costs under control.