Without any specific reason, Blizzard has removed four maps from the main game modes in Overwatch. This is just a part of the changes coming to the game in the latest update to the PC version of the game, coming later to consoles.
Four maps are out of the rotation from Arcade's Deathmatch and Team Deathmatch: Hanamura, Horizon Lunar Colony, Temple of Anubis and Volskaya Industries. All of them are still available in Custom Games. The patch also solves some audio problems in the new Junkertown map.
Blizzard's team is also trying to further balance Mercy's abilities after the big redesign from earlier this month. Check the full patch notes down below.
General
• The credit that Mercy's Resurrect contributes toward her on-fire meter has been adjusted to account for the recent changes in its functionality
Arcade updates
• Hanamura, Horizon Lunar Colony, Temple of Anubis, or Volskaya Industries have been removed from the Deathmatch and Team Deathmatch map rotation, but can still be selected in Custom Games
UI updates
• Made several adjustments to the spectator camera to improve the viewing experience
General fixes
• Fixed a bug that caused the audio from Junkertown's front gate to play when previewing and opening Loot Boxes
• Fixed a bug that prevented the stagger and knockdown VO from canceling active voice lines
• Fixed a bug that allowed an incorrect voice line to play when firing D.Va's Micro Missiles
• Fixed an issue that caused the spectator camera to lose track of heroes and player-controlled objects (e.g. Junkrat's Rip-Tire)
Hero fixes
• Fixed a bug that prevented Genji and Mercy's ultimate voice lines from functioning properly when the Oni or Winged Victory skins were equipped
Map fixes
• Fixed an issue that caused sound effects to continuously repeat when using a beam weapon (e.g. Zarya's Particle Cannon) to destroy the motorcycle in the attackers' spawn room on Junkertown
• Fixed an issue that activated audio cues that are typically associated with enemy hits when shooting the motorcycle on Junkertown