Here's why:

* Red dwarfs are small and cool: They are much smaller and cooler than our Sun. This means they have a much lower core temperature and burn hydrogen much more slowly.

* Long lifespans: Red dwarfs have extremely long lifespans, potentially trillions of years.

* No giant phase: They never have enough mass to ignite helium fusion, which is the process that drives stars to expand into giants.

What happens to red dwarfs in the future?

Red dwarfs, due to their low core temperatures, burn hydrogen extremely slowly. They are expected to continue fusing hydrogen for trillions of years, eventually becoming even cooler and dimmer. They will eventually run out of hydrogen fuel, but this will happen so far in the future that it is difficult to predict exactly what will happen.

Some theories suggest they might become white dwarfs, but they are so small that they might simply cool down and fade away over an incredibly long time.