Oh they're appropriate (tools the big foam guys have).

Wholesale outfits like Industrial Rubber in Seattle
can slice the stuff, in 4' x 4' sheets, to whatever thickness
you want. I bought several hundred dollars worth of
low bun weight EVA (ethyl vinyl acetate) foam in various
colors. Gave most of it away. Sold some. Still have some.
They let me know my $300 dollar order was more of a nuisance
than a sale for them. And that was 15 years ago.

EVA isn't the only alternative. There are other resins.
What's it used for? Good question. I don't don't know the
answer. Most foam is sold for industrial packing...equipment
padding. Stiff and dense and heavy is good in that context.

I dont' think there is much market for the ultra-light low
bun weight stuff, else it would be easier to get. But it
does exist. You just have to buy enough of it to get it.