A portion of the complexity comes from fixing bugs not at its root-cause. Once you have accumulated many such proximate fixes it becomes quite expensive to fix the bug at the root-cause level. The resident root-cause bug continues to create new problems downstream.
Great point. I chuckle at the fact that 'addressing the root cause' is what naturopaths and 'holistic medicine' practitioners are selling themselves on... Claiming that modern medicine is focused on selling drugs to mask symptoms and doesn't address the root cause... Though their solutions are often even more superficial on average... Besides maybe their approach vitamin deficiencies and supplements.
Not much different from biological evolution.