Yet Socrates knew people who could write. He was educated, important, living among literate people. And yet we have nothing. Contrast with Jesus, who lived and worked among the illiterate poor, and it is a suprise he didn't write anything? As for coming long after Socrates, what difference does that make? Do you think literacy rates had changed much? Or that Galilee was filled with more literate people than Athens? Or that the disdain for the written word compared to word of mouth had changed?
Again, miracles and myths are in lots of biographies, from the life of Pythagoras to that of Apollonius. Myth in histories doesn't make them worthless as histories. It means that the ancient genre of history simply wasn't as reliable.
Most of the people in Jesus' world couldn't read, and even those who could usually valued the spoken word over the written, which was often mistrusted. The best way for Jesus to pass on his message was the same way John the Baptist, Socrates, the early Rabbis, and countless others had and would later: gather followers and teach orally.