Hair texture quality, among other texture qualities.

[KisaiTenshi]

Always they are done like that and then reduced the size. That's why i don't understand why so many gaming companies slack providing HD textures.

To avoid a repeat of "ugh the game is too slow" and "ugh the loading time takes forever" and "ugh omg why is this download 50GB"

The textures in the game are a compromise between all three. Not everyone has a SSD to install the game on, and not everyone has 8GB video card from which to be able to use them. If you look at GPU-z you'll probably find less than 1GB of the video memory being used, because that -is- what the average video card has. A lot of crappy video cards have 2GB, it doesn't make them capable of actually using larger textures. Depending on the generation of GPU, it can vary significantly. DX9.1 is 2k x 2k max. DX9_3 is 4k x 4k, DX10.0 is 8k x 8k, DX11 is 16k. And until DX12, there is still a limit of 128 textures.

128 textures works fine in a Single player game, but not a MMO where everyone wants to be a snowflake. You work around this with texture atlases, so that you get more out of one texture, at the cost of effectively making the "texture" smaller.