Here's why:

* Size: Supergiants are stars that are significantly larger and more luminous than our Sun. They can be hundreds of times larger in radius and thousands of times more luminous.

* Stage of Life: Supergiants are stars in a late stage of their evolution. They have exhausted most of their hydrogen fuel and have expanded dramatically.

* The Sun's Classification: The Sun is classified as a yellow dwarf, a type of main-sequence star. This means it is still fusing hydrogen into helium in its core, and it is considered to be in its prime.

While the Sun will eventually become a red giant, it will never become a supergiant. This is because it is not massive enough. Supergiants typically evolve from stars with several times the mass of the Sun.