In office IV/moderate sedation is NOT for everyone of course.
Aside from those who just are not bothered by dental treatment there are patients with medical/health issues that should not have IV sedation. Patient's with ASA status III should only be seen in a hospital setting. Patients that cannot get an escort; patient's that cannot walk up a flight of stairs.
Here are some of the reasons patients give for dental phobia or anxiety or stress about the dentist:
Blogging for Better Oral Health
American Dental Society of Anesthesiology
As well as Modern IV Sedation Dentistry
Master, College of Conscious Sedation