There are few studies on vitamin IV therapy, but there is some data that shows their benefits. One study detailed vitamin C could potentially be an anti-cancer agent when given via IV in high doses.
Chronic dehydration is also a big problem in the United States, especially among the elderly. People over the age of 65 are 20-30% higher risk for developing dehydration. Dehydration can cause low blood pressure, seizures, kidney stones, UTIs, and heat injuries.
The FDA regulates dietary supplements as food, not as medications. They do not approve dietary supplements for safety, effectiveness, or correct labeling before they reach the shelves at the grocery store. Taking a vitamin IV in some ways is safer than vitamins on the grocery store shelves because it has been approved by a medical director and your medical history is taken before administration.