Vattenfall, please explain yourself

I just moved, and started to compare prices for electricity. Vattenfall has a great number of options to choose from. You can choose with what method the electricity you’re buying has been produced. Nuclear, wind, water or “basic” (=nuclear, fossil, wind & water). Now, the pricing for wind generated power is a bit higher than for the other options, but what was really surprising was that the “basic” option, which is powered by fossil fuels in addition to clean energy is priced the same as electricity that has been generated 100% from water power.

My question is, why the hell does Vattenfall have an option that includes fossil fuels when there is a clean option at the same price point?