Why do naked singularities form in gravitational collapse?

We investigate the key physical features that cause the development of a naked singularity, rather than a black hole, as the end state of spherical gravitational collapse. We show that sufficiently strong shearing effects near the singularity delay the formation of the apparent horizon. This exposes the singularity to an external observer, in contrast with a black hole, which is hidden behind an event horizon due to the early formation of an apparent horizon.