Why people say “bless you” when you sneeze

Hardly would someone sneeze without the phrase “bless you” uttered from some one around. It is polite but why do we actually do it?

there is no one particular answer but an article by The Sun UK gives many possible reasons.

1. Some people thought you ran the risk of sneezing out your soul whenever an attack happened, so saying “bless you” offered some protection. This dates back a long time too, and comes from a period before people realised nose tickles were just an issue with the body.
2. There was also a line of thought that the devil could steal someone’s soul when they sneezed.
3. Many also feared evil spirits used these moments to rush into the body so “bless you” could save you.
4. Some say Pope Gregory started it. He became pope after the man before him was killed by the plague in the 590s, and it’s thought he used to say “God bless you” whenever someone sneezed around him.
5. There was once a school of thought that people actually DIED for a brief moment when they sneezed. Uttering “bless you” apparently encouraged the heart to start beating again.

Which one of these reasons look tenable? Or is the phrase just a way for people to remark on a sneeze?