Because truth hurts. It is not a sugar coated movie with a message. Imtiaz Ali made this movie as raw as possible.
In theater I heard many negative comments and people yelling at screen because they were deeply trapped in this corporate race and the movie really hits hard so many are not able to digest so they took blue pill and criticized the movie and got back to their life.
But some people connected to the movie and they thought about this rat race trap by taking red pill. These people liked the movie very much compared to the other bollywood mindless masala movies. Read below article on the movie