The world of painting, and illustrating had evolved very drastically by the time the camera was invented. Perfection was key for portrait paintings, as was most illustration, and every other form of art being produced at the time. Then the camera came out, and both were changed forever.
Suddenly the need for perfection wasn’t as crucial in paintings, and illustration. So artists brush strokes, and lines loosened up, and have continued to do so for the most part since then. This gave way to paintings being able to convey much more emotion, having much more expression that would have not happened if it were not for the invention of the camera. This however also led to appreciation to painted portraits.
The mechanical world produces things that humans are incapable of producing. Yet as humans, typically the things that they are best able to connect are to no surprise, have a very human feel to them. Some art critics even go as far to argue that this is the only true form of art. This first began after the start of the printing press, and the camera was the next step up to this. Up until this there was nothing really to give such an appreciation since most things considered art then had been in fact done by hand.
This camera eventually gave a new element for mixed media. Some of the best photo collages use paint or some for illustration combined with them for a very unique look and feel.