The idea that there must be a plaintiff accusing of crime or civil violations in order for adjudication to occur is absurd.
The offering of complaints is meaningless. In that case, there must be a permanent station of those who sue for even the slightest violations, responsible for upholding the law not only when a citizen by happenstance gets angry enough to sue, but also just by the mere injustice occurring freely in a world governed by laws.
There are district attorneys but how many? Responsible for all, for upholding the law? An impossible task. Justices wait for cases as citizens wait for justice. Who wants to go to court for every rupture of the law? And if this is required, why so many barriers to ease in making and filing a case pro se?