Having the same issue - at first I thought I had messed up something in the settings, but apparently this is normal behaviour. Just paid over €1000 for a Surface Pro 2 with Win 8.1 - I expected a lot of the bugs from Windows 8 would have been worked out by now. However, I believe this feature has been intentionally omitted to make the desktop experience worse than the preferred Metro experience, as has already been suggested. Personally, I am not even getting a pop-up keyboard when I open the Search charm when in Desktop or Metro mode (with Touch keyboard folded back). Is this happening to everyone? This is extremely frustrating as the keyboard icon is obscured by the search bar on the right side of the screen so it is impossible to even manually call it up from the taskbar.
While I am all in favour of progressing the Touch UI, it simply isn't ready for mainstream work at present. The applications in the Windows store are severely lacking, and even the mainstream apps are extremely buggy. I have a brand new machine and have used a number of apps (Twitter, IE, Facebook, LastPass, OneNote, EverNote etc.) but they all feel clunky and are missing a lot of features of the desktop counterparts, so I find myself continuously switching back to the desktop.
Don't get me wrong - I love the Surface and I think it has a great future as a proper work tablet, but this crippling desktop experience is extremely frustrating. I would hope that Microsoft will respond to this feedback positively as these seem like relatively small issues that impact on an otherwise highly competent device.