The primary purpose of data classification is to determine the value of data to the organization. This helps in defining protection levels, access controls, and risk mitigation strategies.
Option A (Regulatory compliance requirements) is important but not the primary reason. Compliance is a result of data classification, not its purpose.
Option B (Facilitating DLP rules) is a secondary benefit, but classification is broader and not limited to DLP.
Option C (Prioritizing IT expenses) is unrelated to why organizations classify data.
Thus, D is the correct answer, as classification helps organizations prioritize data protection based on its value.