Without reproduction, the species would be gone after just one generation. Reproduction is not necessarily the most important thing to a particular creature, it may be happy to just spend its time swimming and eating, but it is the primary goal of the genes within the creature. Good instructions for creating an organism that is good at reproducing get passed on to further generations. If the instructions were poor, the organism will not reproduce, and the instructions will be lost. Only the good instructions get passed on.
Natural selection is very much at work at filtering out successful instructional strategies.
One could say that an organism is only the means to continue the flow of genes. A gene that programmed its organism to be poor at dealing with the environment would probably not be passed on to the next generation. Only those genes that create organisms that are successful in the environment get passed on. If the environment stayed constant, then evolution would have finished millions of years ago, but the environment is not constant. The genes mutate every once in a few million reproductions.