TressFX is developed by AMD and is now on its third iteration, i don't think CD did much other than implement it in their game, and if it looks great, why not? After all, Lara is an important part of how the game looks overall. The same tech is also being used in DE: Mankind Divided:
And since square enix has a marketing deal with AMD, TressFX is probably going to be used a lot in their games. Very much like what Nvidia have been doing for a while in "Nvidia powered" titles. it's not just for looks but for marketing purposes as well, but it looks great to me so i am fine with it