I don’t know what the real purpose was, but in order to draw German forces from their Eastern Front, the Dieppe raid would have had to establish a perimeter and hold it for some considerable time.
In keeping alive or creating the threat of an invasion/future invasion as a possibility would have caused the diversion of some troops. The key thing was showing Stalin that the western allies were doing something...whether or not Stalin would have thought it as ‘enough’ is hard to know for sure.