According to The Verge resource, Microsoft did not include the notification center in the operating system due to lack of time for development.
The presence of a notification center is typical for most mobile operating systems, but it is absent in Windows Phone 8. The reason for this is that the company simply did not have enough time to bring the system to mind.
When a message arrives, an alert bar appears at the top of the screen with a brief description of the notification, by clicking on it, you can open the application and find out the details. When there are several alerts, the strip disappears. In all likelihood, Microsoft originally planned to create a panel where several relevant notifications will be visible at once.
As Thomas Fennel explains, after receiving a number of comments from developers, the company is already working on implementing the notification center in Windows Phone 8.
