It was decided that game engine development was over complicating the goal of Blender. It detracted from actual 3D software development resources and trying to make all blender features seamless with it was nearly doubling potential work.
I believe in the open-source world, this is called "mission creep". It means when a project gradually expands its scope and mission until it becomes unmaintainably broad.
Default Cube is a playable character in Super Tux Kart, although unofficially through a user created addon which can be downloaded through the game’s addon feature.
I've considered "what does the download/install look like" before realizing "You've had Blender installed and passively updating for months [pacman] without using it. Stop that"