I think this topic is akin to saying that you shouldn't bother carrying or practicing with a ferro rod or friction fire, because carrying a lighter is easier and quicker. While this is true, the reason you familiarize yourself with other skills is in case your ideal tool or method is unavailable.
Of course a tarp, space blanket, garbage bag will be quicker to construct with less energy used, but what happens if for some reason, you don't have your tarp? what happens if for some reason your tarp was torn badly and rendered useless? It would be unfortunate for you if you did not know how to build a sturdy shelter out of natural materials, or if you did not have the tools to do so.
Anyone with common sense, takes with them the ideal materials to support them in what they are doing. But if they are knowledgeable about how to make do without there ideal materials, they will be able to SURVIVE when all or most of there gear is lost, or ruined. That is the idea behind survival and bushcraft, being able to accomplish a task using various methods. Like some people back up there equipment, a survivalist/bushcrafter backs up his knowledge and skills. But, just because you know how to do something primitively doesn't mean that you wont bring modern materials and tools to make your life a little easier.
ETA: looks like Thomas Linton beat me to it. Yes, just think of Murphy's law.
EETA: Sicily - looks comfy!
