He went to say goodbye to Katniss out of respect for her and her family.
The goodbye he gave Katniss is different from the one he gave Peeta.
Explanation:
Peeta's father went to say goodbye to Katniss because he had so much respect for her and because he already had feelings for his mother and knew how she was suffering. It was a mixture of respect and empathy.
This goodbye was different from the goodbye he gave to Peeta, who was a more homesick and sentimental goodbye.
