> In order to maintain themselves, autonomous agents must typically observe (i.e. acquire information about) their environment, and then respond in different and ‘appropriate’ ways. For instance, a chemotactic bacterium senses the direction of chemical gradients in its particular environment and then moves in the direction of those gradients, thereby locating food and maintaining its own existence.

rsfs.royalsocietypublishing.org/content/8/6/20180041

Why in philosophy, that beings want to maintain their own existence, is it because only existence has meaning, essence and other properties, whereas nonexistence have none of these?

Or asking in another way, does there exists beings that do not mind becoming nonexistent?