> First, not all applications need it, in many cases you want to do just a series of operations in a single starting number, and you don't need anything else, like if you are for example calculating a factorial, if you need only one factorial, it is useless to make it more parallel.

Sorry for nitpicking, but calculating factorial can certainly be parallelized. Easiest way to do this is multiply every n-th number on each core and then multiply n results together.