To me there are two types of schedules, which I'll call the bean counter schedule and the marketers schedule. It's embodied in the traditional appointment book, with each day cut into one hour intervals. You can block off several hours for a single task if you need to, but by default you change what you're doing every hour.
Most powerful people are on the bean counter's schedule. It's the schedule of command. But there's another way of using time that's common among people who make things, like creatives. They generally prefer to use time in units of half a day at least.
When you're operating on the creative's schedule, meetings are a disaster. A single meeting can blow a whole afternoon, by breaking it into two pieces each too small to 'put the running shoes on' in. Plus you have to remember to go to the meeting.
For someone on a creative's schedule, having a meeting is like throwing an exception. It doesn't merely cause you to switch from one task to another; it changes the mode in which you work.
There's sometimes a snowball effect. If I know the PM is going to be broken up, I'm slightly less likely to start something ambitious in the AM. I know this may sound wacked, but if you're a creative, think of your own case.
Each type of schedule works in its own world. Problems arise when they colide. Since most people operate on the bean counter's schedule, they're in a position to make everyone work with what they are comfortable with. But an effective leader acknowledges this conundrum and they know that some of the people working for them need long chunks of time to work in.
Those of us on the creative's schedule are willing to compromise. We know we have to have some number of meetings. All we ask from those on the bean counter's schedule is that they understand the cost of a meeting.