I was wondering what are the purposes of intubation?

Many: Intubation refers to a procedure whereby an anesthesiologist or other qualified healthcare provider inserts a breathing tube into the lungs. This can be performed during surgery that requires general anesthesia. Intubation may also be performed in emergency situations if patients are unable to maintain spontaneous respirations. Patients in the intensive care unit may also require intubation.

Securing the airway: During general anesthesia and other comatose states the breathing tube allows to pass the required gas mixture - oxygen, air, anesthetic - and to minimize the chance of anything undesired entering the lungs ( blood, stomach content etc.).

Safety: Intubation is done to secure the airway in patient who has been rendered unconscious. With intubation we can breathe for the patient and protect them from aspiration.