For some time I've wondered at the difference between dialogue in drama and in fiction. Though there are parallels I've never been quite sue they are the same. Apart from the obvious differences, such as fiction using 'he said / she said' and so on, and dialogue in drama providing almost all the structure around which action is built, I think there is fundamentally something different about the two forms.
Now I must say I love dialogue. Dialogue should move the action along at least as much and probably more than the narrative. Dialogue is what makes fiction interesting for me. Great writers handle dialogue with dexterity and taste, using neither too much or too little. Look at the way James Joyce., or Raymond Carver for example use dialogue within their work. Take away a phrase and the things falls apart. Dialogue gives a psychological location in space and time, it gives history, indeed it makes history live.
So why don't I want to write for the screen or stage? I think I like the tension between dialogue and narrative, the multiplicity of voices that fiction allows, the infinite shades of irony that between them. Maybe it is not so much that dialogue in fiction is different from that in drama but that its is used diferently and to do different things. Narrative provides a different context in which to explore and evoke relationships, different from that afforded by a stage or a visual image of a location.