Because they like breathing.
After all, if the FBI,BATF,DOJ,CIA are in cahoots with the Drug Lords (and they have been for, oh, a long, long time), then you learn to keep your mouth shut.
The reason the Obama Administration is so quiet is because they have done incredibly stupid and illegal actions that have resulted in multiple murders both here and in Mexico and god knows where else.
They are now trying to cover it up.
The reason Issa is quiet is simple timing. It's summer and most people are on vacation and simply not paying attention.
This is going to get a lot more interesting starting in late September
Being that Obama and Holder like breathing too, I hope they won't mind letting the "buck" stop with them on this one.
That's it. And politicians received drug money that's been nicely laundered through banks, who also make money on it. Thus the phony WOD that never ends, never closes the borders, never really goes after the drug lords, etc. Keeps the price high though, probably. More $ for all hands involved.