Offices are even more full of distractions, over which you have far less control.
At home, I can designate my own closed office. I have full control. I can remain distraction-free.
How does that compare to an open-plan office? People constantly walking and talking around you, many of whom have nothing to do with your job. You simply can't control that. You can't control the noise. You can't control being called into useless meetings or getting pulled into senseless distracting conversations. If you're a senior, you might get pinged multiple times every hour by juniors asking for advice, instead of being able to buffer these interruptions once every hour or two. Hard to buffer requests and questions when they are a tap on the shoulder instead of a message waiting in some inbox.