I definitely think Competitive Parkour and Duels need this feature but there is some current issues that are preventing them from adding it because of the way the game is coded.
TL;DR: Possible but needs a small re-code to work easily.
There are two types of Cubecraft game matchmaking, Lobby-Queue and Server-Queue.(Not official names but its what I like to call 'em) A Lobby-Queue game(like Competitive Parkour and Duels) enter players into a queue into a lobby. They wait in the lobby until two players are matched with each other in queue, then they both get sent to the server at the same time. A Server-Queue game(like Skywars, Eggwars, etc.) sends players to servers instantly but makes them wait for players to fill up the game. Using the lobby-queue system, games start faster because of their small size and conjoined queue. But to quick queue its extremely difficult to develop a system that sends players back to the lobby to be re-queued, and get sent to the new game server. Its a little complicated but, players can't be queued while they are in their original server as that server needs to close and they can't be queued while being transferred to the lobby, and code needs to be run to auto-queue players once they join the lobby.
There is just so many points in this multi-step process which is difficult to code and can easily fail. The best solution is to switch to the Server-Queue system as that just sends you to a new server and you wait for players to join. It will result in slightly extended wait times but allow you to re-queue. In addition, if a player leaves after being match-made you won't be sent back to the lobby and you can wait for another player to join.
Sorry for my horrible explanation, there is just so many moving parts and so many problems that need to be solved for this to work. If you have a question or need clarification, just let me know.
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