Why don't constellations switch places?

It will change. Now the division of constellations is not quite the same as before. Because the twelve planets in the solar system are all in motion, their positions are different. Although our earth is also in relative motion, because of the different revolution and sub-rotation time of each planet or transverse star, their positions on the ecliptic will change.

However, a person's constellation mainly refers to the planetary movement when he was born. Even if the constellation division changes in the future, I don't think it will have any impact on people who have already been born. It's just that the constellation of the upcoming BB is not quite the same as ours.