Why do I have to re-install Alliance of Valiant Arms?

Hello. I have the AVA webpage as one of the pages that open when I open Chrome, so I noticed that they finally added the Infection mode. (zombies) and added the Galil MAR. Then I went to the IJJI Reactor to- of course- update the game! But when I came to, the Reactor told me that it was not installed, and that I had to re-download the installer. Bullchickensh!t! I re-installed the game, so I hope it would work. Any reason WHY this had to happen? Thanks.