We have been; the majority of everyday life decisions, short-term and long-term, is born from rational self-interest.  To imply we cannot self-govern is to imply we can make no decision of our own; if this is true, that none can self-govern, then we should not pretend that a government of elected officials who also cannot self-govern can manage to find the capacity to govern others, a far more difficult task, nor should we pretend that they make our every decision for us, for if they did, what need do we have for democracy?