3 Answers

Can you even begin to imagine the problems if no one died? Just trying to feed the world is a monumental task. Think.

You can also, for a spiritual discussion, turn to the Holy Bible. You needn't read further than the first few chapters of Genesis.

1. If man lived forever, there would be no need for procreation and even if there were, there would not be enough space for everyone. Look at China. They kill baby girls because they are under a one child limit and everyone wants a boy. That would be the world if man lived forever. 

2. Accidents happen. I believe there is no such thing as an accident. I believe everything that happens was meant to happen mostly because of karma or cause and effect. Death happens because man is mortal. 

According to the Bible man and all animals were immortal at Creation, however Adam sinned and now people and animals are mortal and all die eventually. As the period between Creation and the Fall was at best only a few weeks, this state of affairs was ephemeral to say the least.