SMB, it's a matter of meeting US (or Canadian for that matter) requirements for street use. I beleive, and stand to be corrected, that emission testing is part of that criteria, hence the abolishion of 2 strokes.
All the pics you are seeing are Euro models that do come fully equipped for the road. If this gear was left on machines by US importer, they are subject to fines and forced to remove the machines from the country....these Gov't types play for keeps. I don't think you will ever see a Pampera come into the country in street trim...this however does not necessarily stop the "motivated" from converting them once landed (customer that is).