Role of geometric kernel

why cad softwares like solidworks,solidedge,nx and manyothers which use the same kernel, have different levels offunctionality or some have features and options others dont have(in features like freeform,boundary surface,loft,sweep,..). is itbecause some dont use the full potential or are there complementarycodes specific to each one, running parallel with the kernel?
generally discuss the role of geometric kernels in cadapplications.
thanks.
SolidworksGeneral