Bleed air is expensive. You've already paid (in fuel and hence cash) to compress and heat the air and then you're dumping the heat into the spinner. There is also less air to push out the back.
You also have the complexity and system weight of transferring the hot, high pressure air forward into the spinner and then finding somewhere to dump it without creating further losses in the gas path.
Pointy spinners also look sexier.
Avionicar - I've seen some pretty hard looking rubber for sale in select Amsterdam retail outlets.