From what it looked like to me, you at least need a Crafting Table to get components of any sort. So you'll have to grab everything, haul it with you, or to a "home base" of some sort. And sure, some people will want to rob every single place blind...but since *everything* (pretty much) is able to be used in crafting in one way or another...other than out of either sheer challenge, or sheer boredom, why would you go around robbing everyone? In previous games, when scrap metal was harder to come by, I could see stealing it. But in FO4, when all the scrap will be everywhere, and multiple things can be used for the same purpose, I don't see the need to rob *everybody*. Sure, if it is a faction I don't like, or the item is an easy swipe - maybe.
We still don't have any idea how the Karma System (if there is one) works in FO4. Will thefts cause you to be disliked by the faction you stole from? Maybe only if you are caught? Will you care?
How do we know components are weightless? Maybe Bethesda gave everything at least some weight - appropriate to what it is. Sure, you can snag everything in sight, but it's going to weigh you down. Of course, Settlement Components might be handled differently (as those would be rather heavy) - but we don't know.
In the end, I'm a pack-rat. I'll take anything not nailed down, unless there is a good reason not to. In New Vegas, I'm currently not stealing because one of my modded followers complains when I do and, well, I'm trying to romance her. But otherwise I'd be taking most everything in sight if it was worth the trouble of hauling it. The question is, what did Bethesda do in the game to make some things not worth hauling around? Are some things just too dang heavy compared to their usefulness? Are there in-game penalties that make hauling things too much of a pain? Do we eventually come to a complete halt if too over-encumbered? Or, perhaps, our Armor Rating drops as we add on weight, to simulate not being able to move out of the way as easily? That would put a damper on being too weighted down.
We will see, when the game releases, just what checks and balances are in there. If there aren't sufficient ones, you can bet I'll strip some places bare - and even take the nails if I can.