Why is it sometimes difficult of types of software maintenance to distinguish between them?

Distinguishing between types of software maintenance can be challenging because many maintenance activities often overlap in their objectives and processes. For instance, corrective maintenance (fixing bugs) may involve modifications that also enhance functionality, blurring the lines with adaptive or perfective maintenance. Additionally, the context of changes may vary, making it hard to classify them strictly into one category. This complexity is further compounded by the continuous evolution of software, where updates often serve multiple maintenance purposes simultaneously.