It works very well, because the Microsoft Store was trying to operate as other locked down stores do by enforcing better practices. Store apps used to have to use the new permissions system for example. 10S was locked down for security and even encouraged it after they dropped the cheap devices to help bolster secure environments on your own, Microsoft also benefited through control of the Store. They aren't mutually exclusive.
So yes, the security benefits is the issue. Once you impact people's ability to install Chrome and give it full permissions, they scream. 10S didn't allow this, and Google (just using them due to popularity and because they weren't trying to be malicious here either) didn't give a damn about adhering to the new app format's restrictions on permissions.
So yes, the security benefits is the issue. Once you impact people's ability to install Chrome and give it full permissions, they scream. 10S didn't allow this, and Google (just using them due to popularity and because they weren't trying to be malicious here either) didn't give a damn about adhering to the new app format's restrictions on permissions.