Why is a travel authorization via ESTA required for VWP travelers?
U.S. legislation required the Department of Homeland Security (DHS) to implement an electronic travel authorization system and other measures to enhance the security of the VWP. ESTA adds a layer of security that allows DHS to determine, in advance of travel, whether an individual is eligible to travel to the United States under the VWP and whether such travel poses a law enforcement or security risk.
