Wanna know why there are loose ends? Because everything was a dream except when Cobb wakes up in the end.
Inception was about a man sleeping on a plane for 10 hours and dreaming about his family and how his wife's death had been tearing up his heart. He was struggling to come to terms with whatever happened to Mal. When Cobb wakes up at the end, where's the briefcase? Where is the IV tube running into his vein? Every other time we saw someone wake up from a dream, all these key elements were there.
Lastly, Cobb had his wedding ring on at all times except after waking up on the plane. The wedding ring symbolizes Cobb's inability to let go and move on. The top at the end is all red herring.