Staff in hospitals reminisce about how much calmer their jobs were when they return to unit after a smoke break. Without this privilege, hospitalizations are more onerous and less successful at preventing relapse. Studies have shown that people with serious mental health concerns fare better when they have access to tobacco.
Nicotine is a neurotransmitter, not a drug, more easily fabricated by the plant tobacco. It sticks to receptors ordinarily controlled with acetyl-choline and leaves them in place, leaving more acetyl-choline to other receptors that use it, but not nicotine. Taking nicotine out of the equation when acetyl-choline retention may have gone down leaves people in pain and irritable. Not an ideal condition for therapeutic progress.
Alternate sources for nicotine stabilization are inauthentic, ineffective, and in most cases incredibly wasteful. Why can't we have our choice of breath when we need the stability the most?