Why no assasinations?

What's with this taboo on assasination that the US government seems to have?  Why is it such a bad idea to send a covert unit to kill the leader of your enemies instead of carpet bombing the whole damn country, causing the deaths of hundreads of troops and civillians and costing billions of dollars? 

Assasination is a fuck good idea!  Why discount it in whole?

massive collateral damage

I hate the toning down of language to make something seem more acceptable. "Collateral damage"? Fuck you, it's "dead civilians". Same shit applied for "casualties", "kill boxes", "radiation enhancement devices", and whatever other stupid euphemisms the military come up with to protect your precious sensibilities.

Have a problem with reality? Deal.