Only if you want to!
OK, I can see what you mean and I understand, I think.
Clearly you aren't going to argue that the DM is not free to work such things into individual games. I think you are pointing out the flaw that these restrictions place on mindsets.
By that, I mean that by setting up explicit rules to enable certain actions, you are implicitly denying other actions. In turn, this infects the mindset of players and DMs and inhibits the tendencay to run "outside of the box".
Using your immovable rod idea: Sure, Spring Attack makes some sense to do this type of thing. I might not run it that way, and you probably wouldn't either. But, we both seem to have a fair amount of RP experience outside of DnD3E. As such, we may be more comfortable running "outside the rules". We would probably come up with a variety of ways to adjudicate that particular situation. Many of them would _probably_ have a low threshold, but would retain a feeling of danger. In short, we would reward the interesting idea and the willingness to take the risk by allowing it to be suitably heroic.
However, there are probably a fair number of DMs out there that would simply say: "No, it isn't in the rules that you can do that."
There may be even more players that might not even consider such an action because it isn't "in the rules".
Am I understanding your concerns correctly?
If so, I concur. This is a problem that is inherent in rules-heavy systems. At the same time, the rules help establish a nice baseline for anyone, experienced or not, to work with. As I see it, the rules have been baselined by WotC. I don't necessairly agree with all of their decisions, but if I am looking for a new player, and they have been playing DnD3E, we both have a good idea of what to expect. With that strong baselining, there is a lot of common ground wherever you go. If you have the PHB, you can easily determine what is a house rule between different campaigns. This makes it a little easier for the hobby to spread, at least in theory.
However, you do bring up a good point! It is one that I will mull over in my head. Perhaps my player's aren't as creative because they think that they can't do it if iti isn't in the book. If so, I need to improve my DM skills and my communication skills!
