Mainly because there is no story line.
There is nothing to look forward to at the end of the game except an escape scene.
And none of the characters have any personality except for the black guy...
And that's only because of his one line when he picks up Pain Pills.
"Grabbin' some pills."
It's alright gameplay. But I wish they put more THOUGHT into it.
It's just mindless killing.
Eh, a guys game I suppose.