The issue specifically with Viera and Hrothgar are their unique head features. Miqo, legolambs, and potatoes have larger ears but they aren't large to the point they can't be accommodated by a very minor change. (though Miqo glasses are a bit wierd since our ears are actually higher up on our heads than most races) They're also still small enough to also be hidden by various types of headgear as well.

At the same time part of my thoughts can't help but wander to the notion that the majority of the headgear complaints about Viera/Hrothgar are a combination of people upset that the very specific pieces they want to use weren't made visible on them and others simply doing the Whiners Can Be Losers Superfriends bit. "Batman and Robin have utility belts, Solomon Grundy wants one too"

That said, they could have at the least made sure to include Viera/Hrothgar headgear models for gear introduced after the races were added. However going back and making the models for the entire pre existing catalogue feels like a large amount of wasted time and effort. At the most possibly just do research/surveys to find out what pieces are the most popular out of the items predating the races being used as glamours and do those. That would essentially avoid making hundreds of headgear models just to have only a couple dozen actually see use by the player base.