Redundancy is only one way to increase reliability. For example, having redundant elements can allow you to use cheaper components and meet the same level of re

Redundancy is only one way to increase reliability. For example, having redundant elements can allow you to use cheaper components and meet the same level of reliability as a single, more expensive component but at the cost of mass (or vice versa). Most often, there are reliability requirements that are defined at a very high level, and a reliability engineer helps determine the right tradeoffs to meet those requirements. In addition, some of the points of failure don't lend themselves well to redundancy, like release mechanisms. For certain risks, like human-rated spaceflight, they may just have requirements like "no single-point failures", which means redundancy is a must.