I could never understand why the stuff is not usually available in the warm climates.I mean afterall it's main purpose in life is to insulate and I know you guys sometimes need protection from the heast.
I think that may have to do with how the foam is typically used. New construction here is usually 2x6 or 2x4 exterior walls with fiberglass insulation. Attic spaces may be either fiberglass or blown-in cellulose. Those methods are the cheapest, easiest to install, and perhaps the most effective for those types of applications.
As I understad it, the foam is typically used to insulate walls of basements, or perhaps retrofitting to the exterior of an older house beneath new siding. Basements are extremely uncommon here in arizona. My guess is only 1 out of 1000 houses has a basement. I suspect florida is the same way. Basements were never needed here because houses didn't have non-forced-air furnaces because heating was not a priority and forced-air technology was available before most houses around here were built.
People do use foam around here for the retrofitting of older masonry houses. Foam is attached to the exterior wall, and then the foam is coated with stucco. The foam used may be the pink or blue type in 1" sheets, or more commonly a yellow foam sandwiched between two sheets of reflective foil. The foil acts as a radiant barrier, and is more effective in areas with high sunlight intensity. The only foam I can find around here is the white beaded foam, blue foam in 1" thickness, and the foil-clad foam. I simply do not see where there would be much demand for 2" pink or blue foam around here based upon typical construction practices.
Also keep in mind that using foam for a layout is a relatively new idea. I was mostly out of the hobby between 1995 and 2004, and prior to 1995, very, very few people made layouts out of foam. Now, the majority probably do. One can still use the old plywood method, and that is still what I prefer. It's stronger, and better suited to those of us who handlay track. I still plan on using foam to form my mountains, though.
Foam has its advantages - it's lighter, it is less messy, and quicker. It's better suited to those who live in apartments or condos and don't have the space to cut a sheet of plywood or who don't own or like to use power tools.
Kevin