You'll have to talk to Gavin and the others than maintain test net if you want answers to that.  They have repeatedly requested that people not mine on test net because it raises the difficulty, making it impossible to test with.  If we unleashed 20 TH onto test net for even 24 hours, it would make it unusable for everyone else.  Feel free to disagree, but this has been an issue for a couple years now, please go research it.

Yes, I am going to shrug off this invalid point because we are not now and have not been testing ASICs on the live network, so it's an immaterial argument.