What's causing traditional tracking methods to become less effective?

The correct answer is that shifting privacy regulations and changes in technology will restrict access to user data for measurement. New privacy laws (like GDPR and CCPA) and browser changes (like the deprecation of third-party cookies) are making it harder to track users across websites and apps, thus reducing the effectiveness of traditional, cookie-based tracking methods. An increase in conversion window time would not inherently reduce reliability. Browsers like Safari are actually limiting, not facilitating, third-party cookie usage. While ad blockers exist, they haven't led to a decrease in overall digital device usage.