The US, for various reasons that primarily relate to privatized healthcare and a proliferation of lawyers, had absurdly high rates of lawsuits and liability around driving. Most road signs here are excessive for the purposes of making it as straightforward as possible to assign liability to a driver in the event of an acccident.

A prime example of this is the "No U-Turn" signs all over the US. People make U-turns at these spots all the time. The sign is really just there to ensure that any accident resulting from said U-turn is always, no matter what, the turner's fault in a legal sense.