Almost no libraries out there have inline assembler magic. If you wrote a library with inline assembler, you'd have to write it for arm & i386 so that developers could still use it in the simulator. There are very few people out there competent in both assembly languages who are also iOS developers. The need is also pretty low because if you want fast computations, you'd do it in the GPU. The only need might be some bit-banging code for interfacing with external hardware. So the only people who might need assembly are making complicated interface hardware.