I'm sure no one wondered why Dumbledore wanted to die but I give you the reasons anyway.
I don't own Harry Potter but if I did none of these reasons existed and Albus would have been VERY MUCH ALIVE!
"Severus please kill me! I'm done with this life! I can't bear it any more."
"If you produce enough reasons for your wish then I shall, with pleasure!"
"Ok then here is my list of reasons."
1. My life sucks!
2. I killed my sister.
3. I dueled my best friend-turned-enemy.
4. My brother wont talk to me.
5. Minerva never understands why I keep giving her candy.
6. That Potter keeps sticking to me like a lost puppy.
7. My former student now darkest wizard of the world wants me dead and I taught him everything he knows and even all those things he doesn't know!
8. I'm tired and I'm old and women are no longer attracted to me.
9. Voldemort called me a Puppet Master!
10. I am known to be manipulative.
11. Harry smashed all my favourite devices last year.
12. Fawkes keeps burning.
13. Rita Skeeter keeps writing lies about me. I swear I heard her saying that she's gonna publish my lies when I die!
14. People call me old fool despite my wisdom.
15. Hogwartz is getting boring.
16. Ministry is even more boring.
17. I never found the Hallows until when it was too late!
18. Everyone keeps asking questions and expecting answers.
19. Students always snigger every time I make a speech at the start of the year!
20. Phineas keeps criticizing me.
21. Hagrid is half a troll and I never knew!
22. I can't walk easily any longer because I keep tripping over my beard.
23. Umbridge threw me out of my office last year and although she never stepped in here afterwards, still her stink is remaining in my office.
24. Harry says I don't understand anything.
25. People write stupid romances about me like Albus/Severus, Albus/Grindleward, Albus/Harry, and I can't take it anymore.
26. Some Muggle author said I'm gay and that my name is taken from Bumbleebee!
27. Rosmerta keeps calling me "Albus, darling".
28. I ran out of sherbet lemons on Harry's second year of Hogwarts. Probably the Basilisk ate all of them.
29. Harry always guesses my passwords and I'm no longer safe in my office!
30. I put on an ugly ring and burnt my hand at this old age!
So Severus please kill me and let me get rid of this life! Please save me fro…Severus? Are you listening?
Snape: khooorrruuuu khooorrruuuu
31. And my underlings fall sleep when I'm talking to them!
And so Dumbledore got suicidal and drank the potion Voldemort had put on offer for free.