First, from the artist side, I've heard many artists say you can't paint decent picture if you don't paint from real life. Paintings created from photos are not authentic, lack creativity, suffer from lighting and perspective issues, etc. You must observe and paint and draw from real life, in real settings. They claim you simply cannot paint a good lion if you have never been to Africa.
On the other side, I've heard many non-artists say they think artists who paint from photos are just copying the photos. They think we simply try to reproduce the photo as is, sometimes poorly, so what's the point? Just frame the photo!
Well, I'd like to argue both points a bit. While it may be true that your lion painting would be better if you could paint from life while on an African safari, I really don't think that means your art is bad if you don't. Absolutely stunning paintings have been created from photographs, often of zoo animals, by many artists. Case in point, the snow leopard. I've seen many beautiful paintings of this amazing cat. But I'd bet money that most artists who have painted snow leopards, including those who claim good paintings can only be made from live observation in the wild, have never seen a snow leopard in the wild. They are extremely rare and elusive animals. I'd bet almost all snow leopard paintings have been created from photos taken at zoos and wildlife preserves, or made up from various reference.
So, my point is, nice paintings can be made without painting from real life in natural settings.
On the second point, that non-artists believe that artists who paint from photographs are just human photocopy machines, I'd like to argue that too. Here's my recent example. It's a painting I did of a young cowgirl somewhere out west, maybe Wyoming, on a horse and ready to start rounding up cattle. She is too young to do this alone so her dad is coming with her. But she is young and eager while he is older and does things at a more relaxed pace. She has gone ahead and is now waiting impatiently for him to catch up so they can get started.
Did I take the reference photo for this painting from actual cattle ranchers in Wyoming? No. I live in Washington state, near Seattle. I don't really even have a good place to observe WA cattle ranchers. Does that mean I can't paint a picture of a young cowgirl in Wyoming?
It might be true that my painting is not as accurate or "authentic" as it would be if I had been born and raised herding cattle in eastern Wyoming. But does that mean my painting is terrible? I don't think so. I think artists can create wonderful paintings from reference using their talent and creativity. After all, if you can only make a nice painting from exactly what you see then you really are just a human copy machine.
Which brings me to the second point again. We, as artists, mostly use photos for technical reference like anatomy and lighting. We use photos for inspiration. That does not mean we copy them as is. I don't think I've ever copied a photo exactly as it was. Even if it was a great photo, there's something to "edit" out when painting. There's a distracting fence in the background of that horse, or a branch across the deer's face, etc. Removing elements like that is the minimum an artist should do. But sometimes the changes can be much more dramatic.
Here is the actual reference photo I used to create the above painting.