Ken is right. The
IICRC is OWNED principally by regional trade associations, not the other way around.
Trade associations are rather too dynamic for most insurance companies to consider them a viable "group" in their close definition. Members are free to join, and quit, at will. Without any real track record of commitment. The cost to administer those who would join to get insurance, and then drop their membership, is rather high.
Associations do however often gain relationships with carriers to offer members many other types of business liability insurance. The insurance companies give a reduced rate based on their savings to acquire profitable access to interested parties as a decent size group.