In the early days, what was the main purpose if photography?

Before photography, visual arts was one of the only way to capture the world. Famous artists painted portraits of significant people and beautiful landscapes which are very time consuming. I would say photography in its early days is simply a realistic window to see the world and the people in it. The inventors of photography believed that photos are no longer drawn by hand, but "written by light".
An article on petapixel says: The use of cameras has allowed us to capture historical moments and reshape the way we see ourselves and the world around us.

What it's saying is that colored pieces of canvases is a piece of art

They needed different and opinions