As patent portfolios age, the core concept of the original claims can be used as a framework for later claims to track what competitors are doing. Using continuations, the core concept of the claims can be modified by broadening (removing aspects from the claims) and narrowing the claims (using the additional disclosure that was not initially the focus of claims in earlier patents).  By doing this, numerous patents and claims of different scope can be drafted over time that are tailored to exactly what your competitors are doing. This can turn a single patent into a formidable patent portfolio that can be difficult and very expensive for your competitors to prevail against.