That "ignorance is bliss" is so prevalent among humans is a fascinating study in itself. Why are we so prone to fall into this harmful trap? The answer is obvious, though we are often too proud to admit it. We are, in fact, simple-minded creatures. Our brains are not very good at handling complexity, and the reality of the world is that it is incredibly complex, to the point of being beyond our comprehension. To cope, the human brain adopts a necessary strategy -- simplify. A common example of the kind of simplification that our brains employ is the "rule of thumb". Rather than figure out precisely why something happens, which would require delving into impossible complexity, we look for patterns. We select and use the most evident patterns to explain what we wish to understand. Finding patterns is something our brains do relatively well, to the point that we often find patterns that are false and misleading. This is the inherent danger of simplification -- it usually leads to false and misleading "rules of thumb". The conundrum is that we are practically forced to simplify, given our feeble brainpower.
Take science as an example. We tend to think of science as our crowning achievement. What do humans do when they do science? They probe the complexity of the world, look for patterns, and try to reduce the patterns into simple formulas. If those formulas can describe the complexity that we are aware of, we cry "eureka" and claim to have the answer. Eventually, we discover that there are patterns that we didn't recognize that the formulas can't account for, and we are forced back to the drawing board to address the additional complexity. Either that or we simply cover up the anomalies and refocus our attention on the successes of our existing paradigm, which is more often the case, and oh so much simpler. Newton's "law" of gravity is a classic example. Though the average human can hardly fathom this formula, scientists marvel at its simplicity and usefulness. Yet human understanding of gravity is woefully inadequate and primitive. We really don't even know what gravity is. Alien spacecraft regularly demonstrate a mastery of gravity beyond our simple "rule of thumb". So what do we do? We ignore it, we dismiss it, we cover it up, and we point to the successes of our understanding of gravity. Foolish humans.
The complexity we are faced with is indeed daunting. We don't even understand ourselves. For as long as humans have existed, we have tried to understand how our bodies work. All we have come up with is a progression of less and less ridiculous "rules of thumb". The average human cannot even fathom the chemistry of the Krebs Cycle (also known as the citric acid cycle), which is only one chemical pathway in the huge symphony of chemical reactions that makes us function. Is it any wonder that we have been so reliant in the past on the grossest simplification our brains can conceive of, the very epitome of the "ignorance is bliss" philosophy -- that "God" did it?