Many pilgrims want to arrive in Santiago on their first Camino, even if they have only limited time. They therefore choose to start closer to Santiago, or further away but then skipping several stages, for example by taking a bus or a taxi.
A large number of these pilgrims take the road again another year, because they really liked it and now they want to do the "whole" Camino (Many pilgrims mean by that: from Saint-Jean-Pied-de-Port, or Roncesvalles or Pamplona. Others mean: from home). So they slowly work their way back (example: first year Leon - Santiago, then Burgos - Leon, then Pamplona - Leon, etc.) or they walk their first Camino again, but now entirely, without buses, taxis or hitchhikes.