Two possibilities:
1. When you mold something you have to leave a way for air to escape the mold. Those little fingers of rubber are the result of rubber pushing the air out of the mold vents.
2. They could be "vortex generators". When air hits such an obstruction, it eddys around and can exert a tiny but measurable push against the back of the tire. The amount of force exerted is a function of the surface speed of the tire and the speed of sound so, if you're riding relatively slowly, you'll want longer vortex generators on your tires. When you see TDF riders get a tire change at the start of a climb, they're not be fixing a flat, they're getting tires that have longer vortex generators.
Take your pick.