Help with coupled inductor using Partsim
If you wrap a coil around a magnet do you get a battery and free power for life? No you don't. For exactly the same reason you don't get anything out of a transformer with just DC applied. In simple terms, with dc applied to a lossless transformer, the voltage across the primary is zero volts. That means it takes no power therfore it can't deliver any power to the secondary.

In slightly more complicated terms, the primary is still an inductor and that acts as a perfect short under DC conditions.