Most people don't use regional services to travel long distances. And you pay for proper inter-city services.
The point is, if you are in Hamburg, you are no longer in Rostock. So you are only using regional services in exactly one place.
The point is, if you are in Hamburg, you are no longer in Rostock. So you are only using regional services in exactly one place.
Sure, long distances (I had to travel from Rostock to Tübingen last weekend) are typically not taken with regional trains (although you technically can; I did that as a poor student a few times, it just takes 16 hours instead of 10), but over medium distances (around 2–3 hours) you often have both options.