To protect the integrity of each player's experience

"To protect the integrity of each player's experience and create an equal playing field for allplayers, those with ultrawide monitors will be able to get their game's display expanded to 19:9 (the maximum width of the limit zones in games) with a vignette on the sides of the display," Blizzard wrote in an official forum announcement. "We acknowledge that players have put a lot of money into to build their 21:9 hardware setups and seeing barred black screens can be very frustrating for them. Therefore, we'll continue examine these discussions and possibilities for solutions that don't alter the way that games are played."