An external conflict is less easy to observe than an internal conflict.

External conflict used to be the primary form of conflict in genre or popular fiction. Only in more literary works did heroes grow, change, or even question themselves much. Your genre fiction protagonist knew he or she was a better person than the villain and had no reason to change. So the tension in the story was all about whether the hero could outwit or outfight the villain at the climax, which made for rather shallow characterization. 

Yes, an external conflict is not as easy as observing an internal conflict.