Why isn't notifications dynamically pop up as soon as they occur as in facebook.I need to refresh page in order to see the notifications.
Because that's annoying and distracting. This is not Facebook, so we try to keep those things to a minimum whenever possible.
No, you don't. All you have to do is click on the notification banner (the gray box that pops up). That will cause the new content to load in place immediately.
In this way, we get the benefits of automatic updates, without the annoyance and distraction.