Former WWE performer/official Bruce Prichard recently revealed some information behind the cancellation of the King of the Ring event on an episode of "Something to Wrestle With" during a Q&A with fans. Apparently, Vince hated the idea because the event didn't really make all that much money and also because the summer months were rather slow for him financially.
The King of the Ring events started from 1985 - 1991 with untelevised events and then were aired on PPV from 1993 until 2002. Since then, there have been other King of the Ring tournaments in 2006 with the finals taking place at WWE Judgment Day (and Booker T winning), William Regal winning the tournament in 2008 in a one-night tournament on RAW, Sheamus winning the crown in 2010 on RAW and finally Bad News Barrett winning it in a WWE Network Exclusive event.
Vince McMahon didn’t like it. It was probably our lowest sales pay per view of the year, which is crazy because in the territorial days, the summer months were money months and for WWF the summer months were slower months. The Pay Per Views during the summer didn’t do all that well, and King of the Ring wasn’t a large grossing pay per view, so Vince wasn’t really excited about it, and decided to change it up.