There is increasing evidence that having people together in the same place is a vital condition for the kinds of serendipitous interactions that lead to breakthrough innovation.@emollick
The link leads to a paper in PDF format, you have been warned.
I'm not a huge advocate for the return to the office en masse, but I am one of those who need to be in proximity of other people in order to think, make, or achieve breakthroughs.
The office as a concept needs to evolve. Instead of being a place where people go to do work, it needs to become a catalyst of culture, and an environment which enables greater work to happen.