The point is, one needs to verify with ATC. If you depart on the DP and turn left and the controller(s) were expecting you to turn right on course, there is a problem. Of course, the pilot is held responsible. Although most of the time ATC does an excellent job, controllers make assumptions and sometimes give too little information. It's our job as pilots to make SURE we're not only doing the right thing but to ensure we're on the same page as ATC.
