Why do workers whose performance is only to process information in some way or the other, still have offices, and sometimes in pretty expensive places?

Couldn't an IT company be totally virtual? How would the work differ in such setting?

For my working group at my present employer (a start-up) we are discussing about the possibility of granting the right to work exclusively from home, if we wish to.

Our work performance is only to process information in some way or the other, some are programmers, other are data analysts or technical writers.

How would the work flow be influenced?

I see that people won't have to spend time commuting, so that makes in some extreme cases, +3h each day for some employees. It's clear that they won't dedicate 3h extra if they telecommute, but that means less costs for them and less stress. Or, has face to face some essential property that we can't ignore?