It's not a duplicate but it's for the same reason I explained in this other question: targeting WP 8.0 app to WP8.1 app?
Bottom line is you're still targeting Silverlight and not the XAML for WinRT which is where the new controls are.
Question
I finished targeting my Windows Phone 8.0 project to 8.1 but the ToolBox Controls are still the same like 8.0 xaml controls
for example : the new DatePicker
control
Then i did the following
The Windows Phone Silverlight Components tab isn't showing any 8.1 Controls
But!, The Windows and Windows Phone XAML Components tab is showing all the new 8.1 Controls (And they are all checked)
But why i am not seeing them in my ToolBox ?, and they don't appear in XAML code too
Solution
It's not a duplicate but it's for the same reason I explained in this other question: targeting WP 8.0 app to WP8.1 app?
Bottom line is you're still targeting Silverlight and not the XAML for WinRT which is where the new controls are.