A full set boolean queries, while useful for specifying a query, are likely far too computationally expensive at scale. The reason you don't see most major search engines abandon them is because the resources are better spent investing into heuristic algorithms that benefit a majority of the userbase.
While I am still personally a huge fan of Google's work in this are and many others, sometimes I long for the days of straight boolean search queries in search engines. I could often find exactly what I'm looking for, and get the same result each time.
Are there any other major or effective engines that allow for boolean queries beyond AND/OR?