Here's why:

* Low-mass stars (like our Sun) are not massive enough to overcome electron degeneracy pressure during their collapse. They become white dwarfs, which are supported by this pressure from tightly packed electrons.

* Medium-mass stars (slightly larger than our Sun) also become white dwarfs, going through a similar process.

Neutron stars form from the collapse of high-mass stars (at least 8 times the mass of our Sun).

Here's a breakdown of the process:

1. Core Collapse: When a high-mass star exhausts its nuclear fuel, its core collapses under its own gravity. This collapse is incredibly rapid and violent.

2. Neutron Degeneracy Pressure: The core becomes so dense that the protons and electrons combine to form neutrons. This creates a very dense, compact object called a neutron star, supported by the pressure of these tightly packed neutrons.

Therefore, only the most massive stars end their lives as neutron stars.