mainly because it cant be "infinitely dense". the limit is the size of the nucleus of the atom. IF all the electrons are stipped away, AND all the space between the nucleuses were removed, there would be a certain amount of space the matter would have to take up. even if space within the nucleus was removed, it would still have a limit. This would leave the size of the star a few miles in size (for a very large star), which would make it a neutron star. when it turns into a black hole, it gets even smaller than that. Much smaller.

the more man learns, the more he realises, he really does not know anything.