KenK,

There are always more specialized tools to do a specific job easier. The value of a good knife is that it's a very generalized tool (possibly THE most generalized tool), that may not do all the jobs as well, but it WILL do them. Since you're unlikely to have all the specialized tools in a field emergency, having a generalized tool can easily become a lifesaver. This is why the current thought in "survival" knives is that the more general-purpose it is, the less specialized it is, the more tasks it will do, the better.

Part of the answer to your question about the value of cutting wood is not just shelter, but fire. When it's been really raining for some time, the only dry wood to be found may well be... inside the wet wood. Sometimes deep inside. That, and the need to fabricate things out of wood (traps, stakes, handles, shelter, whatever) amounts to a critical distinction from a "hunting" (skinning) knife, which is seldom if ever called on to deal with wood.