Internet Explorer is the browser that's so nice they created it twice, once for Modern UI and a second time for the desktop. These two dispirate browers are based on the same code, but have different sets of tabs and windows, making them function as two different programs. Windows 8.1 adds some neat features to Internet Explorer such as unlimited tabs and multi-window support in Modern UI, but it leaves this artifical wall between the two versions of the browser.
Chrome for Windows 8 has just one browser that allows you to switch between Modern UI mode and desktop mode by changing a setting. Better still, when you switch back and forth, all your open tabs and windows are preserved. Why hasn't Microsoft done the same?