More of an issue about focus.
Editors build and prune the directory. Not public-facing tools to search it.
But licensed user of the directory data can add whatever features they wish.
Google have added a nice search feature to their licensed copy of the ODP data, as have Gigablast.
Though Google in particular is often working with a copy of the data that is several months old.
Out of the many hundreds of licensed users of the ODP, it's surprising that so few have added a search feature as it is an often-requested feature.
Why not ask a few more and see what they are capable of?