Modular hardware breaks down into reusable parts. When one part fails or must be upgraded, it can be quickly replaced with another of the same or similar type, without disrupting everything else. Usually this is impossible without a clear and widespread hardware standard supported by many manufacturers over a long time and many similar models of the same hardware product.
Modularity and reliance on standards is part of any healthy signal infrastructure, because it reduces the amount of obsolete hardware that will become toxic waste. When such waste is electronic, it is often referred to as e-waste.