There are several theories as to this. First, there is the fact that they wanted to make some parallels between Raskolnikov and the journey of Jesus. Additionally, there is the fact that the journey was the prize, rather than the destination. The struggle makes the man, not the destination, in other words. It also allows the reader to identify with the main character as he makes his way into and out of various scenarios, thus increasing the shock value when things don't go the protagonist's way.