I don't think that bacteria act as pre-programmed robots, at least not in the sense we normally think of robots, as automatons without consciousness or awareness. I eat to stop the pain in my gut. I only go to the bathroom when I feel the pain of excrement waiting to exit. I don't try to defecate because it feels good. I would say that the pleasure one gets from eating and defecating is simply the feeling of relieving pain.
Pleasure is just a nice additional benefit.
Freud would emphatically disagree with you here. But first I beg you to reflect and to reconsider your own life here as a clear case in point. I assume you do celebrate it. When I think of pain I usually think of cutting my finger, doing homework or yard work, or getting up early on Sundays. My point is that hedonism requires life, and so living is a more basic drive than hedonism.