Why is science inherently fallible?

Science is fundamentally based on two things, observation and reasoning. But no matter how carefully we observe, we do not observe everything, and no matter how carefully we reason, we do not think of everything. Human beings are fallible and therefore our intellectual creations such as science are necessarily also fallible. Despite the inherent fallibility of science, it has still proved to be quite useful, as should be apparent to anyone who is using a computer to read this answer. Science can fail, but quite often it succeeds.