Others may have tried these components before. Component developers not smarter than others, but their official assignment is to build them. Efficiency again a product of Dedicated specialization. Opportunity for component maker to optimize, research algorithms. Consistency - possibility of a regular, coherent design.
Reusable software is a way to preserve the inventions of the best developers.
When a software element has the potential for reuse, it becomes economically attractive to use the best quality-enhancing techniques. If design is separate from the implementation, risk reusing incorrect or obsolete products. With a Command class and a history. Source Code - economic and psychological impediments. Violate modularity rules.