Like most outdoor sports, rafting in general has become safer over the years. As a result the difficulty rating of most river runs has changed. This may be the reason Croatia is not well known for this particular activity. Although it does have wild and exciting rivers. Up to grade 3 that flow through sceneries that will take your breath away.
Additionally, white water trips can promote environmentalism. Because of their positive outdoor experience. It contributes to the economy of many regions. Which, in turn, may contribute to the protection of rivers.