According to Skype, the reason is because Microsoft has started integrating more of Qik’s features into Skype, and because of that, Qik is no longer necessary as a standalone app, which is why they have decided to shut it down. “Since then, we have learned that many of you are already doing these things in Skype, and as a result, we migrated some of Qik’s most used features into the Skype app you already know and love.”
Skype reassures users that their platform can do the same things. “We’ve enabled video messaging in Skype and fun features such as filters, to make your messages even more personal. To send a video message in Skype today, simply look for the video message icon in the media bar.”
That being said, Qik’s last day will be on the 24th of March, 2016, and as Skype notes, you will want to make sure to save any messages you consider special or worth saving, because after that the app will no longer be available for use.