I gotta be honest. Off the top of my head I can list the starting QB, 2-4 RBs, TE, and at least the top 3 WR's for every single team. I'd be lucky if I could name more then 2 linemen for any team other then my team (Philly), or maybe a couple of our closest rivals (NYG, Wash).
I suspect the vast majority of us are the same way. I can acknowledge that such information could have usefullness, but what good is kowing the backup when you don't know jack-s about the starter? Why would we wanna clog up the depth charts we all use with info almost none of us will use?