I believe foams are used on the nitro cars because of the extra HP and weight and they hold up and last longer, a set of rubber tires in a 20 or 30 minute main would make for some interesting pitting.
my problem with foam tires is they come to dang big right out of the package and you have to cut them down, for me, this is a big psychological waste of money and tire. if the foam tires came out of the box a bit smaller i wouldn't feel like i'm wasting so much of the tire, foam tire on pavement in electric, is faster and cheaper, but as i've been told, its not traditional so we can't do it.