Here's why:
* Many stars are much larger: There are many giant and supergiant stars that are significantly larger than the Sun.
* Red dwarfs dominate: The vast majority of stars in the Milky Way are red dwarfs, which are much smaller and cooler than the Sun.
Therefore, the Sun is considered to be a medium-sized star when compared to other stars, but it's actually on the larger side compared to the majority of stars in the galaxy.
