Because Fluent calculates many fields as they're needed and the .dat file only contains the data Fluent needs to run. For CFD Post use a .cdat with the fields you want, or add additional data to the .dat file. Note Fluent can't read a .cdat file as it doesn't contain what Fluent needs.
Hence my suggestion to use Fluent post processing for Fluent models.
You are navigating away from the AIS Discovery experience