How do people know to type "bm:" for Bookmarks? Google? Is a Google search now part of the UI's workflow? Or will people simply stop using Bookmarks because it is so obscure (you're seeing this with mobile browsers, Bookmarks are hidden so go unutilised).
Ditto with Windows. In Windows 9x you had a nice UI for search that allowed the user to: Search file/folder names, search within (contents), and to filter by file type and file date(s). In Windows Vista+ it is now hidden strings like "filetype:" (and that is the least obscure example, try doing the between-dates thing WITHOUT googling how first). Plus now "unknown file types" cannot be search within at all (even if you alter the indexer's settings it no longer works, you have to add each file type in the registry as a "text file").