To me, there is a simple answer to these questions. If we answer by asking the following question,
a controversial question 20 years ago:
Why using windows instead of the traditional command line shell?
Today, no one would challenge it back again. In 20 years from now, the same thing will happen again for a holographic representation of the file system, maybe?
Until now, the 3D world in the perception of the public was limited to the gaming industry or to some very specialised and costly software used by very high technological industries.
Until the point where software such as Second-Life, Vista from Microsoft or Beryl for POSIX system appeared.
There is no doubt that the growing performance of computer will encourage such a development in all fields of computer software.