Using the Command-Q keyboard shortcut to quit an app does not work on Minecraft. It never has and the bug has been reported multiple times. It works in the launcher but not once you've logged in.
Linked issues
duplicates 1
Comments 3
Can someone please read my comment on the other issue? This really needs to be fixed, and I have perfectly good reasoning behind it, but no one seems to be watching the issue. https://mojang.atlassian.net/browse/MC-594
Duplicate of: MC-594 - Please use the search function to see if your bug has already been submitted.
Currently 27% of tickets are being closed as duplicate.