The reason companies didn't work with VRML was, quite simply, because they didn't get it. The IAML spec will be published and freely available to anyone who wants to use it. Vizbang founder Ancona says that he believes people will eventually want Spark to support VR standards. At this point in the standards development process, however, most customers don't care about VR standards. It also allows programmers to bypass much of VRML 97, if they so desire.
Programmers are free to create any number of other profiles that can plug into the Core Profile.
The Core Profile is much lighter weight than the full VRML spec. Other optional profiles are implemented as software components to be downloaded as necessary. Thus, X3D defines a modular architecture with no huge, monolithic VRML plug-in to complicate use, programming and innovation. With X3D, the user only uses the profiles needed to view the current content. Similarly, when content creators test their content, they only need to test with the profiles needed for that specific content, not with a massive VRML browser that may have many features they don't need.