WHY IT ISN'T THE DEFAULT - is anyone's guess.
It's quite obvious, actually... it's not the default because it doesn't work as well for most people. Verbatim is good when you're searching for fairly specific terms, spelled correctly. If you're asking a more general question, with words that may appear in many variations, or if you don't spell well or are lazy, then the "new" Google works dramatically better.
I think a lot of complaints about Google search today, especially by people who have been around for a while, really boil down to the fact that the old search tricks don't work very well any more. In the early days of search we all learned how to create effective search queries, by picking carefully targeted search terms, combining them in particular ways, omitting any extraneous or "filler" words and lots more that make search queries look very different from natural language. But the search engines (or at least Google) have been changing along with the user base, which is now comprised of almost entirely non-technical people who haven't been using the web for long enough or heavily enough that they learned to compose searches that catered to the engines' weaknesses.
So, today, Google focuses on optimizing for the now-common case of search queries which are most often natural language questions, typed quickly and carelessly. The search engine tries hard to figure out what the user meant, rather than what they said. To those accustomed to being very precise and saying exactly what they mean, this is somewhat infuriating, because they don't want the machine to guess at what they meant, they told it what they meant. For the average user, though, who is more accustomed to dealing with people, who are good at guessing what is meant, the new system works much better.
Personally, I've adapted to the new reality. I tend to type complete sentences for my search queries, framed as questions, including typing the question mark (not because I think it's useful but just because I'm thinking a question sentence, so my fingers emit a question mark). I also don't worry much about typos. I find it works very well, often much better than what I can get with an "old-style" query, with or without "verbatim".
(Disclaimer: I work for Google, but on Android, not search. All of the above is just my personal experience plus speculation, not inside information.)