I believe it doesn't matter, as the chance of choosing the door with the car is 50%.

From a logical point of view, yes, but in reality, it's not the case, and the decision should be changed.
Let's say there are three doors - 1, 2, and 3. The car is behind the first door.
If we initially chose the first door, then we don't need to change our decision to win.
If we chose the second door, then we should change our decision.
If we chose the third door, then we should change our decision.

Therefore, in two cases, we should change our decision, and in one case, we shouldn't, so the chances of winning by changing the door are 2/3.