I think this is the underlying cause for many of the failed projects from the 'Second Life bubble'. Many human activities, especially those related to information intake and processing have a long history of being 2D. From clay tablets to paper books, from the first photograph to 4K television, virtually all of the information designed for human consumption has been 2D. Only an incredibly small percentage is in 3D and even less is designed to be consumed in 3D (e.g. video games are often 3D internally but are designed for 2D consumption). This might or might not change in the future but if it does it will be changing neither soon nor rapidly.

Yes, one can use 2D interfaces inside 3D worlds but any 3D system short of the matrix will have a noticeable quality degradation (e.g. visual fidelity, haptic feedback, fatigue, etc) compared to directly using a 2D interface in real life. A few edge cases might become feasible much sooner, e.g. using VR to emulate large screens but that's hardly 'Virtual Reality'. Until we come up with meaningful ways to represent more kinds of information in 3D and/or create a matrix-style experience, VR will most likely be limited to applications that are inherently 3D.

This obviously includes entertainment (VR games, 'movies', 3D art) and CAD/CAM/3D modelling which are already very much 3D in nature and internal representation, even if they are currently usually projected onto 2D screens. Outside of that, the main 'educational' usage currently consists of building 3D environments (labs, buildings, factories, complex machinery) that emulate real-life environments in order to familiarize trainees with the workflows in those places. This can be surprisingly effective, especially considering how much cheaper VR mockups are compared to e.g. NASA's real-life 1:1 ISS training replica.

These applications are worthwhile in their own right and they will probably be able to sustain a decent market for VR hardware and development. However, I'm personally much more interested in seeing what kind of concepts that aren't already inherently 3D can be enhanced or revolutionized by adding another dimension.