Spinoza presented his work in a proposition/theorem format following Euclid, presumably to varnish his work in the seemingly eternal verities of mathematics.
Is there any significance as to why Plato presented his work mainly as dialogues? Or does it simply reflect that the pre-eminant artform of the time was the theatre, so varnishing his work with the glamour of the theatre. Are his works, not dialogues, but actually a play, where the dramatic tension is not provided by the human condition, but the condition of philosophy?
The SEP entry on rhetoric & poetry in Plato confirms my characterisation of his dialogues as drama:
Plato's remarkable philosophical rhetoric incorporates elements of poetry. Most obviously, his dialogues are dramas with several formal features in common with much tragedy and comedy (for example, the use of authorial irony, the importance of plot, setting, the role of individual character and the interplay between dramatis personae). No character called “Plato” ever says a word in his texts. His works also narrate a number of myths, and sparkle with imagery, simile, allegory, and snatches of meter and rhyme. Indeed, as he sets out the city in speech in the Republic, Socrates calls himself a myth teller.