Following the last entry, I must state that there is a lot of bureaucracy in Germany, and in a few other places too. Spiegel Online, in another article in its inimitable English, helps us to get to the bottom of this:

bq. The average age of students in their very first semester is already a relatively ancient 23, partly due the fact that many students take a few years just to complete the first semester partly due to constant course and university changes and partly due to mandatory military or civil service.

You see that – all Germans have to be in the civil service.

(Thanks to Ekkehard for spotting it)