Induction vs Suggestion : Why is trance important ?

Hypnosis is about achieving an (desirable) effect/change (e.g. stopping smoking / anaesthesia).

Hypnotists (in my limited understanding) have two "tools" that can help achieving the effect : Induction and Suggestion.

The suggestion serves to install an automatic response (e.g. anaesthesia).

In order to achieve this therapeutic effect, how important it is that the patient is in a (deep) trance when she receives the suggestions ?

Why and how is trance important ? Why and how people are more susceptible to suggestions in a trance ? What is the role of a trance ?