Sociological: Nephi speaks in the present tense, but that is not unusual in prophetic discourse. It cannot be determined precisely to which people he speaks when he calls them a stiffnecked people. If it is his own current population, this is a fascinating statement, given the probable small numbers of lineal Nephites at this time, and the probability that their shared difficulties would have tied them even closer to Nephi. Jacob was no less a prophet, and with both Nephi and Jacob in their midst, and the common enemies around them, social science would have expected a very believing community.
Either Nephi speaks to a future population (again a legitimate reading of prophetic discourse) or his current population breaks the bounds of social expectations. As indicated previously, the most likely scenario that would create this change is the influx of a number of gentiles into that community. This provides the best explanation if the statement is aimed at his current population.