Why do ancient poems mostly use images such as going upstairs and taking a boat when expressing feelings of parting?

Some common images in ancient poems have specific uses, such as "willow", "moon" and "pavilion" in farewell poems, "running water", "spring rain" and "spring grass" in hate poems, "wild goose" and "red bean" in expressing thoughts, and "bamboo" and "orchid" in festivals.

The reason why we use the image of "going upstairs" to express our sadness at parting is because we can see the distant scenery, see farther and highlight our parting.

"By boat" is because the ancient water transport was developed and ships were widely used as means of transportation, so the pier ferry often became a farewell place.