Although values are present in GTM, why are some DataLayer parameter values absent in GA4?

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There could be several reasons why some DataLayer parameter values are absent in GA4, including:

1. Different tracking methods: GTM uses a tag-based system to track user behavior, while GA4 relies on an event-based system. This means that some DataLayer parameter values may not be applicable or transferable between the two systems.

2. Different naming conventions: GTM and GA4 may use different naming conventions for DataLayer parameters, resulting in some parameter values not being recognized by GA4.

3. Configuration issues: It is possible that there may be configuration issues or errors in the implementation of GA4, which could cause some DataLayer parameter values to be missing or not tracked properly.

4. User behavior: Not all user behavior may be tracked by both systems, leading to some DataLayer parameter values being absent in GA4. For example, if a user interacts with a specific element on a page, but this interaction is not tracked by GA4, any corresponding DataLayer parameters will also be missing.