I don't get it either.
I actually sat in a management meeting not so long ago, where we all agreed that efficiency and productivity was higher than before (according to our metrics) – and still, one of the people present said that they missed being able to just pop up, look over direct reports' shoulders, etc.
The rest of us confronted them with the fact that all of us – they too – had celebrated our progress moments earlier, and agreed employees delivered better than ever, but we were still unable to totally persuade them.
I find that infuriating, and kind of frightening.
Not only have managers all over the world done things like stuff people into open floor plans (despite the fact that it was never backed by science, and its selling points are now actually refuted by science), and thought that there is something "special" about physical co-location (ignoring the possibilities of video-conferencing for fifty years);
They are now actively going against better knowledge because of their own need for the feeling of control (which they'll never achieve, of course – slackers will slack anywhere), and will continue to use butts in chairs as a metric.