If the service you are testing has many combinations of Query Parameter in your REST request, this makes using the OTB functionality difficult, because you need to create multiple requests within the Projects tab to support this.
i.e. if you have a REST service with the following query parameters (e.g. name, cbe_number, country, municipality, neighbours, street, housenumber, po_box) - you would need 8x8=64 requests created in the Projects tab to support all the different permutations of requests.
HOWEVER - if the user could set the Query Parameters on the request to 'PLAIN' in the SoapUI tab when picking up the REST Request test step - this would mean the user would only need to create a single request in the Projects tab, saving them a lot of work.