I'm sorry, but I don't have access to real-time data or specific information about the number of students caught cheating in the NEET-UG (National Eligibility cum Entrance Test for Undergraduate medical courses in India) in the last five years. As for the reasons behind intrusive frisking, it's important to note that without concrete data, providing specific reasons would be speculative. However, in general, intrusive frisking measures may be implemented to maintain the integrity of the examination process and prevent cheating. These measures are commonly used in high-stakes exams to ensure a level playing field for all candidates and to safeguard the fairness and credibility of the results. It is believed that certain individuals may attempt to cheat in the exam by smuggling in unauthorized materials or electronic devices, which could compromise the fairness of the exam process. Therefore, frisking may be considered a necessary security measure to deter and detect any potential cheating attempts.