I’ve heard that “There was nothing worth conquering” bit before about Ireland and Scotland, yet when one looks at the effort and maintenance required for Hadrian’s wall it is very clear to any impartial person that Rome simply couldn’t conquer the Scots. To build and staff the fortifications certainly was a drain, and it could have been avoided or minimized by simply marching to the northern coast. Even the nuisance raids from the Irish don’t seem to be something Rome tolerated from other neighbors; while Rome probably had the military might to defeat both of these places, they certainly didn’t have it in the right place and time to do so.
Rome was and is the greatest empire of propaganda.