RASP has not been designed to capture many of the dependencies in our corpus; for example, the tagsequence grammar has no explicit representation of verb subcategorisation, and so may not know that there is a missing object in the case of extraction from a relative clause (though it does recover some of these dependencies).
rASP is a popular parser used in a number of applications, and it returns dependencies in a suitable format for evaluation, and so we considered it to be an appropriate and useful member of our parser set.