[Zope] ZCTextIndex - prefix wildcards not supported?

Why are wildcards '?' and '*' not supported at the beginning of search terms in ZCTextIndex? It would be very useful to search for terms using '*someterm'. In the cvs for ZCTextIndex, Lexicon.py (http://cvs.zope.org/Products/ZCTextIndex/Lexicon.py?annotate=1.17.10.2) the code raises an exception for wildcards at the beginning of search terms (see line 113) and a related comment says" 111 # The pattern starts with a globbing character. 112 # This is too efficient, so we raise an exception. Why is this 'too efficient"? Jonathan