No one who is a national from the 36 countries in the Visa Waiver Program needs a visitors Visa if the stay is less than 90 days. You can enter the information on line before your trip and it’s highly unlikely you’ll have any issues (exceptions would be you’re on a do not fly or terror watch list)
Upon arrival, some people may be taken into secondary for an interview to determine the actual purpose of their stay (are they here for free medical care, employment, etc.)
MMMMMMMMMMMM, Lets see for years of me coming back and forth with family and friends over a hundred times with all of us together I’d say that we do need a visitors visa because we have had to fill them out .
You fill out a customs form and a visitors visa, that visa gets put into a passport for your stay and if you overstay your 90 days then you are in violation of immigration laws and therefore illegal