Because more people are retiring than are finishing school. The baby boomers are the largest post-war generation in Germany, and that's coming back to bite us.
Most importantly, companies aren't used to the employment market being a seller's market, so they're not willing to pay competitive rates for new hires.
As result, no one's willing to do 3 years badly paid training (Ausbildung) just to earn below-average wage in a dead-end job.