The Sex Offender Registry includes about 10 times more people than really conceivably pose a threat to re-offend.
They may do more harm than good.
The more restrictions you pile on, the more your system begins to look like permanent probation, which would violate a whole bunch of state and U.S. Constitutional provisions.
They cost the State millions of dollars, trying to keep tabs on those 90percent who pose no risk to reoffend.