This seems like a pretty good explanation of why mip maps are used: https://gdbooks.gitbooks.io/legacyopengl/content/Chapter7/Mip.html

It also becomes apparent why there is a line beyond which the texture would become blurry. Because you have gone past a certain distance from the camera and therefore transitioned to a different mip map.

Of course since it is meant to solve a problem with things in perspective, you might not want it if the things in your image are aligned that way.