I think not all native speakers speak eloquently. It is a skill which is developed through a long period of training and is an inherent talent in some people. It also has to do with people's character, whether they are the extroverted type who like talking to people or the reserved type who speak less.
It is even harder for non-native speakers to speak eloquently when they are not exposed to good English-speaking environment. Being able to speak a second language correctly is quite an achievement by itself. Being able to speak fluently is the next step up for those who have mastered the language.