The dialogue seems to have enjoyed some popularity during the Renaissance and Enlightenment periods, with Galileo, Hume, and Berkeley publishing important works in that form. By the 1800s, though, it seems to be very rare in science, and not common in philosophy either. I'm curious what led to its unpopularity and how gradual the process was. Was it already out of fashion by the time Hume published his Dialogues Concerning Natural Religion?
The dialog was very popular, in a modified form, for presenting socialist ideas in the 1800's and early 20th C. The problem lies in their being mistaken for fiction by later critics. For example, Edward Bellamy's Looking Backward, from 2000 to 1887 is often considered science fiction of a sort. Problem is, it really isn't fiction. It's just the narrator facing no problems but being shown around the future by a bunch of nice people. There's a ton of faux-sf dialogs that used imagined futures or other worlds the way Plato used the tale of Atlantis in Critias or More used Utopia (also often classified as sf).
Dialogues have always been a special form of presenting science and philosophy. Hume published the Treatise, the Enquiries and the History of England (to just name his most famous works) in non dialogue form. I would argue that the format never really was popular.