Comparison to non-biological organisms

To understand why cancer exists in the first place (and why the human body has only evolved "good-enough" tumor-suppression), it can be insightful to compare biological organisms with synthetic machines and immortal organisms. For example, a computer system does not "get cancer" because it is built out of auditable parts, can employ extreme forms of error-correction, and employs other steps to reduce risk of errors (such as running in a temperature range that prevents CPU errors). Biological organisms on the other hand are built out of self-replicating cells, which have higher failure rates and are not easily auditable. Most importantly, biological systems did not evolve with human intelligence and technology at its disposal, or with the resources to let cells extensively audit other cells. Rather, organisms evolved in an environment where it was beneficial to trade off longevity for short-term reproductive gains; it may even have been beneficial to increase the rate of mutation to adapt to new environments (such as deadly diseases), and thus a few extra cancers late in life are not highly selected against by evolution. This is in essence why cancer is more common in biological organisms, and why it may be impossible to entirely prevent cancer without significant and proactive intervention within the human body on a cellular level