...Because of the unknown?
What comes with death?
Nothingness, an empty void, the utter end of your existance, a different kind of existance?, what kind?, does it bring judgement for your actions, or it's just rewards?, do you go on remembering everything that is dear to you or all the baggage of your life is swiped clean and now you don't recognize right from left?
These questions and more are more than enough to make lots of people nervous.

Then of course is the matter of the actual moment of death, people say they want to die in their sleep, not because they are wimps, but because there are a million ways in which your final moments can be very, very unpleasant, the kind that you don't want to experience even for a second, no one wants to die a slow painful death or a violent fearful one, the kind certain cancers bring, or after you get burned badly or if you fall into wrong hands and get tortured beforehand, in a bad accident, in an airplane accident, like my dad; that must have been horrible for everyone in that flight, and not only for psichological reasons, rapid descent does horrible things to your body; some time ago, I heard someone being decapitated in one of those terrorist kidnaping videos (damn them!), the noise that poor soul made when his neck was being cut will assure anyone that that wasn't a good death, poor man.

I fear death because I don't want to depart this world, everything here is too dear to me to want to leave, I don't want to make my loved ones miserable and I don't know what is coming; I hope I'll be reunited with long lost loved ones and I hope that there is reincarnation and that I'm working towards ascending in my karmic wheel, but, I don't know for sure and I don't like uncertainty.