It seems like common sense. The more profoundly someone is in hypnosis, the more suggestible they will be. And, the more suggestible someone is, the more effective the suggestions will be.
However, as with so many things in life, common sense does not apply to hypnosis. Research has shown that a hypnotized person is no more suggestible than someone in a normal waking state. What hypnosis does actually, is make the person more sensitive and responsive to subtle communication cues, like facial expression and tone of voice. That is why master hypnotist and Neuro Linguistic Programming founder, Richard Bandler, emphasizes to his students that for words to have the greatest impact, they must sound like what they mean. For example, if we say the word "excitement" in a flat tone of voice, it will be much less effective in eliciting excitement in listeners than if it said with an excited tone of voice.
As for trance depth, again, common sense is off the mark. Research has shown that a person can accept and act on a suggestion whether he or she is in hypnosis, or not. Advertising is a good example of that. And, effective therapeutic hypnosis can be done with someone in a very light trance state.
On the other hand, individuals in any depth of trance can reject suggestions that do not suit them. Paradoxically, someone in a very deep hypnotic state tends to be generally unresponsive to suggestions. The deepest trances are, however, very useful for anesthesia. The person in a deepest trance will be aware of what is happening, and will be feeling very good, even if they are undergoing surgery. They will feel no pain, and because they are so focused on the good feelings of the trance, they will be unlikely to pay any mind to any suggestions.
So, what is going on when someone responds to a hypnotic suggestion to stop bleeding or eliminate a habit? Remember that someone in hypnosis is more responsive to subtle communication cues. One quality of hypnosis is that it causes the person to be very focused on the words and nonverbal communications of the hypnotist, so a properly formulated suggestion can be accepted and acted upon more readily. A properly formulated suggestion is one meets the personality needs and (sometimes) bypasses the belief systems of the person.
For example, one of my clients who was not showing up at work only went back after I discovered that that he believed that he needed to be there to protect his employees from the other supervisors. Just the threat of being fired was unmotivating. Just hypnotizing him and commanding that he show up at work regularly would have been ineffective. However, the feeling he got from protecting "his people" made work meaningful to him in a way that no simple"Go back to work!" ever could, no matter how deeply hypnotized he might have been. I knew that already, of course, because he had already been unsuccessfully commanding himself to back to work for days.