You still can do that, but in many cases you'd better not say a peep about why.
In my experience, folks tend to give way too much information when they're turning something down. There's a felt need to say something that manifestly justifies you saying, "No," or "Sorry, I can't."
So, the photographer says, "I can't do that, because...", the would-be customer is offended at the "because", and the rest will be a matter of public record. Stopping immediately prior to the "because" is most HIGHLY recommended in these perilous times.
I refuse to do work for liberals or democrats and tell them why to their face.