In the past were there studies demonstrating opioids aren’t addictive if someone was in pain?

I’m trying to understand why any doctor thought opioids wouldn’t be addictive. Were the pharmaceutical companies actually presenting studies backing up what they were saying?

I remember years ago a push for medical doctors to be more aware of the pain a patient was experiencing, and I remember that ridiculous mantra that pain medication isn’t addictive if the patient is in pain. I never believed that, it baffles me why doctors did.

Side note: I am in favor of prescribing these drugs when needed.