I'm going to make up some dumb numbers: suppose people are 5% more productive in the office, but the office has an amortized cost of 10% total compensation. You shouldn't open an office. But say you've purchased an office outright, and maintenance is now only 2% of the cost of total compensation (8% of cost was paid up front). In that case, you would want people in the office.

In the real world, this is more complicated, because you also add in employee preferences as a reason for or against an office, you can't neatly measure productivity, you probably didn't buy the office in cash, you leased it, or borrowed money to buy it...).