With regard to engineering, I am unaware of any studies or even anecdotal suggestions that the public is endangered by the lack a continuing education program.  Notwithstanding the common belief that education is in and of itself a noble pursuit, I would not entrust the State to determine whether an individual is in need of further education, nor more pointedly, the specific nature of that need in situations where a need exists.

The State has entrusted professional individuals, through oath, to operate within parameters which ensure public trust and safety.  It is incumbent upon those individuals to maintain that trust.  If trustworthy entrusted individuals perceive a need to further their knowledge on a specific subject, trustworthy individuals will do that.  Untrustworthy individuals will to violate trust, regardless of their continuing education credits. 

Trustworthy professional individuals are best suited to determine the specific knowledge needed to support the details of their work.