Minecraft Launcher remains open for a long time after closing game

When I quit the game, I expected the Minecraft Launcher to quit immediately.

Instead, the Minecraft Launcher remains open for a long time. I timed it at about 20 secs after Minecraft is closed before the launcher quits. The launcher is the grass block icon that you click to enter the game, as opposed to the crafting block icon that opens when Minecraft is launched.

1. Open Minecraft as usual.
2. Hit quit game on the main screen.
3. Watch the Minecraft Launcher remain open.