Why astronomers continually build telescopes with larger-and-larger diameters?

Telescopes have three functions

1 to collect more light

2 To resolve close objects

3 To magnify.

Explanation:

To collect more light we have to build large sized mirrors ... Then only we can see very faint objects.

To separate two close objects a also we need large aperture

So by making large telescopes we can see more faint objects and more deeper into universe ...