Because the anti-nuclear mindset is too strong in Germany. We are still affected from the Chernobyl disaster (still can't eat wild boar, still can't eat mushrooms from certain areas). The nuclear waste problem is also not solved and extremely expensive. Then there is politics: Nuclear plants lifetime was extended, then Fukushima happened and "overnight" lots of old plants were shut down.

Germany is at 14% nuclear, 30% coal (even though all national coal mines have closed), 10% gas, 46% renewable (wind, solar, bio-gas, water, all without proper energy storage)