While the bulk of enterprises want the ease of SQL access, its difficult to do this with the MapR DocDB (JSON). Currently the only integration is with Elastic Search where the updates are replicated to the index. (Deletes are not, but should be.)
But there is no tool that will allow one to query the index to search a set of documents and tie that to a query against the documents.
Without SQL access and easy secondary indexes, adoption of the hierarchical modeling will slow and be limited.