Question: It happened to me just one time, I don't know how common it is. I wonder why it can happen.

I was hanging at duty-free shops before a flight from Germany to Turkey. I heard the *last call* announcement 40 minutes before the departure time and my name was explicitly mentioned. When I went to the gate, boarding had been completed except me. Normally that airline closes the gate 20 minutes before the departure.

The pilot announced that he was talking to the control tower to take off earlier than planned. At the end we couldn't take off earlier, but I didn't understand why they tried to do this.

Answer: 
Short answer, because they can. The airline makes their own schedule and can change it whenever they want. Departing and arriving early has more upside than downside.

Keep in mind, you must be at the gate *at the original Boarding Time*. Meaning, yes, if Boarding Time is 10:15, they can start boarding at 10:00 if they want and make last call at 10:16. If a passenger is not present at 10:16, they can close the flight and depart. This is rare, but possible. Point being, the only time that matters is Boarding Time, especially if the flight is delayed.\*\*

There are two notable exceptions to this:

1. Slot Controlled airports where the destination airport gives departure clearance. This is however relatively easy to get moved up.
2. Gate space at the destination.

\*\*In some cases, such as a remote stand, they load the bus once, at boarding time. So if everyone makes it through by 1016 and you're no where in sight. The bus, and your plane, are gone.
Weather can be an issue here. If planners are aware of an oncoming storm, it makes sense to get planes out before it hits the airport, or to get planes down a window between weather systems.

In the extreme case of this, you have [Delta flight 431](https://www.washingtonpost.com/news/dr-gridlock/wp/2017/09/13/heres-the-story-behind-that-viral-video-of-delta-flight-431-and-its-race-with-irma/?noredirect=on&utm_term=.b6765ceb6202), and balls of solid stainless steel from the entire team to put a 737 down the gap between an outer arm of the hurricane and the core.