Overtaking your Colleague on Road

Well, it just came to my mind a few days back. I was going at a good enough speed, overtaking almost all my fellow bikers and a few cars as well.

Suddenly I noticed that I could overtake them mostly at a particular time. And it was when they were changing their gears.

And then I thought of checking if same happened to me, and it did. This might not be the only reason but it was just an observation.