Why do they name space shuttles that go out in space?

Answer 1

It is customary to name spacecraft in the tradition of naming naval ships. It is considered bad luck in the military (and with good reason) to fly or travel in a vessel or aircraft that has not been properly christened or named, be it on Earth or anywhere else.

Previous examples were expendable spacecraft (e.g., Mercury, Gemini, and Apollo missions), where each was named individually within its specific mission/program. For example, Alan Shepard's first Mercury capsule was named Freedom 7; John Glenn's Mercury capsule was named Friendship 7, etc. All of the Mercury capsule names ended with "7", indicating the number of the original Mercury 7 Astronauts. With the Gemini and Apollo missions, each spacecraft had its own name, within the mission number.

The Shuttle names continue that tradition, though being reusable, they maintained their original names throughout their history. Only the mission name/number changed.