Having to go to an unexpected meeting really messes with the flow of your whole day.

Yeah, my department in my previous company used to have a daily meeting scheduled for 10am. Everybody would arrive at 9, make some coffee and then lounge around, because nobody wanted to start any real work before the meeting.

The meeting lasted 1 hour, work got distributed, people discussed and called around to gather the relevant info and tools, and then... they basically didn't start, cause lunch was scheduled at noon.

So basically, that one meeting derailed the entire workflow for half the day, and no real work got done before 1pm.