There is no standalone player for Blender that has a license that lets you sell it. So the only way to distribute a Blender game is the Blend file, which requires Blender, which means you're giving everyone with the program to make the game a game to loot and part out. For that reason alone it's worthless.
Python is another reason.
And file corruption, Blender is not a stable enough basket to keep all your game making eggs in. You need a different engine for stability's sake.
Other than that, it's actually capable of better graphics than other poor man's game hackery software, like Unity.