Does anyone have any idea what would cause the throttle to become stiff?Dude.... is this a trick question???

Anna Kournikova always made my throttle stiff.
All seriousness aside, while it could be a cable issue, my first guess would be that the grip glue on your throttle grip has deteriorated, and is perhaps binding on the control housing above it. You didn't say if you had Kuryakyn Iso grips; I do, and recently my throttle grip got a little sticky on the throttle sleeve from old built up RTV silicone I use for glue. It's easy enough to pull the grip, clean it and the throttle sleeve and reglue it.