Why do celebrities wear dark glasses?

If you are a reader of celebrity 'news' (aka gossip) or even the general entertainment section of any news bulletin, you might have noticed that the majority of the celebs are pictured wearing dark glasses all the time, even on a dark winter evening. I always used to wonder why? So here are some possible reasons I have come up with:

1. Its a fashion statement

2. They get paid for it

3. To protect their eyes from flashy press cameras

4. To hide their face with no make up (which is rare)

5. To hide their red swollen eyes due to overdose of drugs or because they were stoned last night

6. To avoid eye contact with strangers

7. To hide true emotions/vulnerabilities which are often reflected through the eyes

8. One crazy person started it and eveyone else is following the trend

9. All of the above