Why are there restrictions on Windows Store app development, such as file illiteracy?

To answer in a nutshell, it's for the safety and security of the end user.

The store app platform has two key features to keep up with the cloud era.
One is the "Device & Services" (or "Mobile First, Cloud First") architecture.
The other is App Reliability.

• "Device & Services" architecture:
  Important logic and data are in the cloud, and devices (PCs and smartphones) are in the front end (shown below)
• Application Reliability
  End users can trust the app. Platforms and reviews restrict untrusted apps from being developed/distributed

These two are related. The "Device & Services" architecture allowed us to limit the capabilities of the device-side platform.

Under the "Device & Services" architecture, for example, databases are placed in the cloud. It then accesses the database with a cloud-side web service. This means that the device only needs HTTP/HTTPS access to its web services, and that the device does not need database access.

Now, once you understand this feature, you'll understand that the platform has removed features that can threaten end-user security or compromise your privacy, such as:

• Reading and Writing Files
  You can "install" viruses or secretly read files related to end-user privacy
at your disposal.
• Database Access
  If you have direct access to a database on your LAN, you can do whatever is allowed for that user. It is also possible to extract all the data and send it to the outside world.
  *Currently, there are third-party databases that can be distributed together with the app. In Windows 10, the database included with the app will be accessible via Entity Framework 7.
• Identify users and devices
  Identify allows users to track their behavior through multiple apps and websites (only within one app can be identified)
• Interprocess communication, Loopback connection
  Allows communication through other servers to be detected by traffic monitoring and not communicated with other programs without end users noticing.

When you think, "Why doesn't this feature exist!?" think, "Can you use that feature to threaten the safety of your end users?"

※ Of course, it is not yet fully functional.If you have an idea that passed the "Test" above, please contact the UserVoice site.

See also the following documents:

• MSDN Blogs: http://blogs.msdn.com/b/b8_ja/archive/2012/05/25/metro-trustworthy.aspx
• TechNet Blogs: "Windows 8 Security Feature #5 Windows Store Application" http://blogs.technet.com/b/jpsecurity/archive/2012/11/29/3535394.aspx
• @IT: "Three Things Metro Style App Developers Need to Know" http://www.atmarkit.co.jp/fdotnet/chushin/readyforwin8app_01/readyforwin8app_01_01.html
• Community Open Day 2013: http://www.slideshare.net/yasuhikoy/windows-cod2013