Going back to my original question, very little response on European countries

but a full overview on the USA.
Does surprise me though that only 20 states have it by law for all drivers, think in Europe for motorcycles it is simply mandatory everywhere. In some countries also clothing has been specified.
Having read all your comments, I can only say that I do not understand why in some countries in Europe an exception is made for trikes, in some countries in combination with a safety belt. The latter absolutely making no sense at all. So in principle we have no argument on that. I am just the "idiot" that really likes to ride without. For all that never tried it, find a private area and try it out. At least you understand what brings us "idiots" to go for this style.
In the end it is everybody's own choice. Discussing about insurances and all does not hold, that can be managed within the rules of the premium to be paid. Fact that this does not happen, is a clear statement. Nobody get on its bike/trike to get hurt. Apart from some daredevil accidents, most of the time we are hit by morons on 4 (or more) wheels who do not pay attention. They should pay a higher premium for causing more accidents?
So let's leave it up to society and most importantly to the individual to manage the choices.
Now back to the first line of this message, here is the current list:yes:
Europe
Holland No Helmet but safety belt
Germany No Helmet but safety belt
Belgium Always helmet
UK No Helmet
USA
Alabama All riders
Alaska 17 and younger
Arizona 17 and younger
Arkansas 20 and younger
California All riders
Colorado 17 and younger riders and passengers
Connecticut 17 and younger
Delaware 18 and younger
Columbia All riders
Florida 20 and younger
Georgia All riders
Hawaii 17 and younger
Idaho 17 and younger
Illinois No law
Indiana 17 and younger
Iowa No law
Kansas 17 and younger
Kentucky 20 and younger
Louisiana All riders
Maine 17 and younger
Maryland All riders
Massachusetts All riders
Michigan 20 and younger
Minnesota 17 and younger
Mississippi All riders
Missouri All riders
Montana 17 and younger
Nebraska All riders
Nevada All riders
New Hampshire No law
New Jersey All riders
New Mexico 17 and younger
New York All riders
North Carolina All riders
North Dakota 17 and younger
Ohio 17 and younger
Oklahoma 17 and younger
Oregon All riders
Pennsylvania 20 and younger
Rhode Island 20 and younger
South Carolina 20 and younger
South Dakota 17 and younger
Tennessee All riders
Texas 20 and younger
Utah 17 and younger
Vermont All riders
Virginia All riders
Washington All riders
West Virginia All riders
Wisconsin 17 and younger
Wyoming 17 and younger