Even when you’re as tough as the guys in "The Cremation of Sam McGee" seem to be, it’s a pretty rough life up in the Yukon. Just getting around is a chore, and it seems like you hurt pretty much all the time. We get a lot of different descriptions of suffering in this poem, most of them having to do with how bloody cold it is. We hear about the pain of dying in the cold, the pain of travelling in the cold, etc. Fun to read about, not a lot of fun to do.
This poem’s focus on suffering gives us a strong sense of a particular place and time, and makes the whole work much more moving.
At the last moment, the poem turns a moment of real suffering into a silly joke, which rewards the characters and the readers for the pain they have been through.