In the olden days, headmasters, clergymen, writers and scholars had 'studies'. Ministers, civil servants and dons had 'rooms'. Doctors had 'consulting rooms.'
Nowadays they all have 'offices', which I think is rather vulgar and undignified. Head teachers and clergy shouldn't have 'offices'. It brings them down from their pedestals.
When I was young, an 'office' was not primarily a place or a room ; it was something more abstract, an organisation or group of people with specific duties. 'The Foreign Office'; 'talk to my office to fix up a meeting'; 'we need to clear that with the Cabinet Office.'
The Americans again, I expect. 'The Oval Office', etc.