Because admins have to answer to the auditors(and our conscience) when they ask the question "How do you ensure that personal and confidential information is not leaked from your environment"
Which is why Windows 10 is my worst nightmare.
But it still installs the entire Windows store with Candy Crush Saga, Facebook, Minecraft, XBOX, etc. and they make it nearly impossible to remove. Why on earth they would force that crap down the throat of their ENTERPRISE customers is beyond me.
I fought with it for months and finally gave up and cancelled the deployment project until MS offers a better way for enterprises to control the Window Store.
Update: Added more below
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IE: When trying to build a secure environment, you must eliminate all unnecessary attack surfaces. The customer did not need "XboxIdentityProvider" installed their Windows 10 Enterprise environment. But this is something MS feels must be installed on all Windows 10 PCs thus they made it nearly impossible to remove.
And I'm not talking about controlling employees here, but simply enforcing settings for compatibility with legacy systems, legal compliance, etc, the list is endless.