Indeed, there is a reason to use the term "affirmative obligation." The law contemplates different levels of duty in different circumstances, and obligations can depend upon whether the pertinent conduct is misfeasance, malfeasance, or nonfeasance. Sometimes, a person can be responsible for the consequences of what he did, because he did it tortiously, but not for what he did not do. Sometimes, he can be responsible for what he did not do, say, because he is a public official required by a statute to do that thing and failed to. Sometimes, he can be responsible only for what he did illegally.

Jokes about lawyers and verbosity are easy to make, but words are the tools of the trade and are usually chosen carefully and carry particular meanings. You might as well laugh at a mechanic for insisting on using a phillips screwdriver in a screw with a phillips head rather than pounding the screw head out of shape by forcing a flathead screwdriver into it. Of course, if the mechanic messes up the screwhead, it might cost him some time and the price of a new screw to fix the problem, but if a lawyer uses the wrong tool, it might cost a client (and ultimately, the lawyer) millions of dollars. Or jail time.