Short answer; because everybody's done their due diligence and decided it's simply not worth it.
That didn't stop a parade of neo-cons from making fools of themselves on the American Sunday morning news shows, but contrary to their alarmist exhortations none of them seriously believe that the events of the past few weeks are the first step of Putin's push to rebuild the Soviet empire.
Putin did what was entirely predictable; he has secured a perimeter around some real estate that is strategicallly important to Russia. As the leader of Russia, that was the only responsible course of action open to him.
All the claptrap about "violations of sovereignty" is not to be taken seriously, especially when it comes from US politicians, who historically have shown far less respect for the sovereignty of others than virtually any other nation on earth, a record that goes back well over a hundred years.
If Yanukovich had been something other than an incompetent dolt, he would have taken strong measures when the Nuland-Pyatt recording came to light. When you are the legitimate head of state and foreign diplomats are caught out planning your removal, there can be only one response.
The Americans should have been sent packing immediately. Instead, Yanukovich did nothing, sending the US the message that he was more concerned with preserving his own hide and his ill-got wealth than he was with leading his nation.
Thus emboldened, the string-pullers in Washington continued to ramp up the pressure, goading their "democracy activists" to ever more egregious acts of lawlessness, a process that has ended quite predictably in the current impasse.
Crimea has been returned to its historical status as an outpost of Russia. The rest of Ukraine is an economic basket case that neither the EU or Russia are particularly interested in nursing back to some semblance of health.
Nor is America. Sure, Ukraine is a great piece of the geo-strategic puzzle, and parking a few missle installations around the country would be a great anti-Russian statement.
But Putin has long seen such gestures for what they are; empty sabre-rattling.
So regardless of the blowhard rhetoric of people like Canadian Foreign Minister John Baird and his French counterpart, what's done is done.
No serious person believes there will be a war over Ukraine.