Top left corner Crack, unable to control via touch-screen

Hi, can anybody provide me a explanation why the top left corner crack(even minor crack) can disable the entire display on the Mi3 WCDMA var.?

I have replaced the display once and now I had the minor crack and my display, again, not reacting to my touch.

I am tired of this prone to die display and I am seeking insight on what is the weakness of this display, why is it so easy to crack and dies?