Why stitch in raw?
Because maybe each image needs slightly different settings to get them all to match and the best way to do that is to have all of the pieces together on the screen at once?
Also because the changes to the raw files individually might be different to the ones you want to perform when you see the scene as a whole?
No problem stitching in RAW in Bridge. Open the RAW files you want to stitch, in ACR. Make the adjustments you think appropriate, such as getting sky tonality and WB matching etc etc. Hit the 'Done' button, lower right of ACR window. Then go back to Bridge and select at the top of the page, 'Tools'/Photoshop/Photomerge, and watch the miracle happen.