What is the difference between having the bar on my shoulders (good morning) or hanging in front of me (dead-lift)?

The bar position makes all of the difference in the world. When you have the bar at a hang, your upper back, wrists, and many other muscles are involved with the pull.

When the bar is on your shoulders, you are weighting the end of a lever where the fulcrum is your lower back and hamstrings, which shifts more of the tension to that area.