From a psycholinguistic vantage point, the term “ignorance” and the term “nescience” have very different semantic connotations. The term ignorance is more generally more widely colloquially utilized than the term nescience and it is often wrongly used in contexts where the word nescience would be appropriate. “Ignorance” is associated with “the act of ignoring”. Per contrast, “nescience” means “to not know” (viz., Latin prefix ne = not, and the verb scire = “to know”; cf. the etymology of the word “science”/prescience).
As Mark Passio points out, the important underlying question which can be derived from this semantic distinction pertains to whether our individual and global problems are caused by “ignorance” or “nescience”? That is, “ignoring” or “not knowing”? It seems clear that it is the later. We know about the truth but we actively ignore it for the most part.  Currently people have all the necessary information available (literally at their fingertips). Ignoring the facts is a decision, an irrational decision, and people can be held accountable for this decision. Nescience, on the other hand, acquits from accountability (i.e., someone cannot be held accountable when he/she for not knowing something but for ignoring something). Quasi-Freudian suppression plays a pivotal role in this scenario. Suppression is very costly in energetic terms. The energy and effort which is used for suppression lacks elsewhere (cf. prefrontal executive control is based on limited cognitive reseources). The suppression of truth through the act of active ignoring thus has negative implications on multiple levels – on the individual and the societal level, the cognitive and the political, the psychological and the physiological.