Ava, they don't trust you. What happens if there's a demon attack and you just happen to be near the scene of the crime? Think they're going to listen to you when you say you were just out getting coffee? Think they won't shoot first and ask questions later?
Have they told you that Sam's been training? Soon he'll be able to use his powers without the blood. With a demon coaching him he'll learn fast. He'll be stronger than you.