Why is this redstone dust not powered?

The redstone lamp is powered, it seems, because it is lit. Then the cobblestone block in the middle should be powered as well with the same logic, but it seems it is not powered because the redstone dust upon it is not.
Why?
The third couple of blocks shows that a powered cobblestone block should power redstone dust that is lying upon it.
Best Answer
I got an explanation in the #mincraft channel on freenode that redstone torches from the side only "soft powers" a block. Sufficient for a redstone lamp to be lit, but not to power redstone dust above it.
A redstone torch from below is on the other hand hard powering a block, also affecting the redstone dust.
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How do I activate Redstone dust?
You must attach a power source to the redstone in order to power it. Power can be transmitted up to 15 blocks away. The light in the redstone dust dims until the last piece becomes completely unpowered. Power carried by redstone will transmit to blocks adjacent to it.Where does Redstone dust power?
Redstone dust transmits power to adjacent redstone dust and blocks, but its strength decreases by 1 for each block the redstone power travels. Redstone dust can thus transmit power up to 15 blocks before needing to be maintained with a redstone comparator or re-strengthened with a repeater.What does Redstone dust power?
It would really be a bummer to see old contraptions break, that's why I have an idea: when placing Redstone dust, you can right-click on it to change it from dot -> cross or cross -> dot.STUPID REDSTONE MISTAKES: How to Fix Them!!
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