The first point I'll make Thrasher is, although it is good to use some items more than others, ie: "exclusively", as you put it, due to the confidence it provides over time, it will limit the number of fish you could catch if you don't mix things up a little. Often fish will ignore one item and hammer another...if you are going to take the route of limiting the number of terminal items you use, I would limit that number to two or three things, rather than just one. My choice, if a pink worm were one of them, would be to complement that with an item that is small, like say, a jensen egg and wool or something of that nature. This will allow you to present two very different looking items, and give those stubborn fish an alternative option if they aren't taking the worm.
Now, as for fishing worms last, well...I'm not certain, as I rarely fish them, but will speculate based on my experience with blades. Often anglers will fish more traditional gear, like roe bags, wool, shrimp, etc...and there are times when fish are present and they won't touch any of these items. In these cases, I will throw something unusual and flashy. Something big, that they don't see so often, and they slam the float down almost like they are angry, no subtle takes here. This is the response I often see when I switch to blades after fishing other items unsuccessfully. They will frequently hammer such items out of aggression, or even frustration. Being so tight lipped through prior presentations, I feel it might have a lot to do with infringing on their space, or territory. Now this is theory obviously, but I think having some large, obnoxious item coming at them after they have been repeatedly "pestered" by common gear all day, causes them to strike out of pure frustration, or anger. This is often why people will toss worms and other similar items last, as although they don't entice the majority of fish, they do get a response from the sulking pestered fish that has been sitting down there all day avoiding all the usual suspects...
In a way, I guess the gear you toss at them is like a circuit within a circuit...many anglers follow a pattern not only in the places or routes they fish, but also in the gear they chuck...
Hope that helps,
rib