Just found this interview from rpgamer site.

Suzuki-san: Whenever we introduce new races, we want to make sure we feature their unique elements. With the Hrothgar and the Viera, because of their unique head shapes, the team actually drew a line in the sand that helmets are going to be a huge challenge to represent and so we don’t want to display helmets. The helmets not being visible is not just because we wanted to show their faces, but more about trying to work with the limitations that we have and work around them. There are elements that are pieces of headgear such as glasses or circlets that people still want to see on their characters, so we did our best in accommodating those elements as well.
So most likely it was a cost and design(limitation?) decision and probably we will never get helmets/hats on the 2 new races.

Source: https://rpgamer.com/2019/09/final-fa...ers-interview/