Redstone dust lies inside what looks like a normal stone block. Is there any specific reason why you need an iron/diamond pick to mine it? It's not like the redstone dust is a hard material. Redstone dust can be broken without any tools so I don't see how that would make the stone harder to mine. I mean, look at Lapiz. It's in what also looks like a normal stone block and drops a dust/powder when broken. Yet, it can be broken with a stone pickaxe or higher.
I'm not complaining or anything. It's just something random I thought about.
Well, the same would go for diamonds, and the reason being is what is inside is more valuable than for example just coal, so I guess Notch thought if you are mining something rewarding,you should have to go through a bit of a harder time obtaining it.
What's easier to do? Picking up fragments of conductive metal with your bare hands or crushing conductive metal into a placeable wire with your bare hands?
I'm not complaining or anything. It's just something random I thought about.