I reckon the OP of it is only limited to the ability of the player. I mean, if someone's a noob, they're good at Eraser and nothing else. If someone's alright, they're good at eraser. If someone's good, they're good at eraser. If someones better than good, they're good at eraser. Then you got MetalSurfeR, Oopla, DSC, Ken, amongst others, that are good at eraser, but get just as many points in pusher or pointman. For that reason, noobs have their eraser to cling onto for some good scores, and the pros don't really care.
Correct me if I'm wrong.