Shadows in main towns causing huge FPS drops (WOTLK; Deathwing)

Hello,
please what is the purpose of all those shadows in main cities? I think players summon them on purpose (to cause other ppl FPS drops). Is it possible to remove them permanently from the game because I think I am not only one who is facing this issue. I think this is also main reason why is WoW ending with error msg. about not enough memory (I know also new textures from WoD take a lot of RAM). I already found tool how to increase amount of RAM WoW can use but I think better will be to remove this shadows from game. Is someone also facing same issues? Thank you in advance for reading and maybe acting.