Why are helmets so small?

Do the makers of helmet think that people with really large heads don't ride bikes? I have found only three helmet that fit my pumpkin head, ICON, full face Mainframe, in 2x fits really well. It sadly had to be replaced do to a spill.

It was replaced by a Fulmur Modular that is a 2x also. The Fulmur was replaced because I wanted a better fit. I replaced it with an HJC CL-MAX which is by far the best helmet I have ever worn.

I have been told that Nolan and Shoie also have 2x helmets, but the problem is that no one locally handles Nolan and no one has a Shoie in 2x that I can try on.

I have several dealers that will order me a helmet of the size that I want, but they want me to pay first and they consider it a special order, so as not to give a full refund.