Why does beah flash back to the last time he saw his parrents

Read the poem "travel" by edna st. vincent millay. the railroad track is miles away, and the day is loud with voices speaking, yet there isn't a train goes by all day but i hear its whistle shrieking. all night there isn't a train goes by, though the night is still for sleep and dreaming, but i see its cinders red on the sky, and hear its engine steaming. my heart is warm with friends i make, and better friends i'll not be knowing; yet there isn't a train i wouldn't take, no matter where it's going. what is the central idea of this poem? the narrator is preoccupied by a desire to travel. the narrator spends many hours traveling by train. the narrator is frustrated by the noise of travelers. the narrator has fond memories of her travels.