Because there are several ways of getting to Venice on the Orient Express. So, say you go by the route of being a pioneer or an elder, missionary, Bethel worker, Governing Body member or whatever - you are prominent. Therefore, you get to Venice being prominent.
But not everyone can do these things. If you cannot do these things, you have to get to Venice by a different route. You'll get there ok but you'll have to clean the toilets. That's the other route, the toilet cleaning route. If you don't get to clean the toilets, don't worry there's plenty of other non-prominent tasks that'll get you to Venice.
They put a map up showing the two different routes.