Its not quite clear why we must die

Its not quite clear why we must die
and suffer agony and pain;
- why must life and living lie
beneath a green and mossy plain?

Some insects, when their joy is done,
croak and die, then sink in rain;
- why lies man in midst of fun,
beneath a green and mossy plain?

Our work not done, our song unsung,
rewarded not for life's harsh strain;
- why lie bones with weeds among,
beneath a green and mossy plain?

If we were made to lie and rot
beneath a green and mossy plain,
why at birth are we not shot,
and sink as bugs in pouring rain?