You might be looking for a kind of deliberate planned game design that just isn't really there in Minecraft.

The world is destructible so why not have a block to blow it up? TNT takes gunpowder to create because why wouldn't it? Gunpowder comes from creepers because they're around and they explode.

Minecarts are for riding in, but the first thing Notch demonstrated for them was a rollercoaster. Horses weren't added until some time later. You can still craft a Minecart With Furnace even though powered rails made them obsolete.