What is the main reason why no red dwarf is currently believed to have naturally reached the end of its life?

Answer

Their predicted lifespans of trillions of years exceed the age of the universe.

The universe is only about 13.8 billion years old, which is insufficient time for red dwarfs, whose lifespans are predicted to last trillions of years, to have exhausted their core hydrogen fuel.

What is the main reason why no red dwarf is currently believed to have naturally reached the end of its life?
astronomystarsstellar evolutionstellar deathred stars