I regularly do !g, but I think the thing that is reducing that fastest is the declining quality of Google results. If I search for ‘x, y and z’, I then see a load of results with small text underneath saying ‘include z?’. It drives me demented, why wouldn’t I want to include my search terms?
Well, I think the answer to your question is Google is trying to be friendly to the layman. It's not hard to think of examples where the user inputs a something into the search box that a CS major knows will not result in the implied wants of the user. Google tries to do a lot of human to machine translation work, and I think you're seeing the result of it. That being said, you can use quotations to explicitly include terms.
A barely related side rant: my microwave decided it wants to error out when it thinks you're trying to microwave air. i have a bowl in there. stop telling me to open the door to put something in. Whatever engineer at GE thought they would be smarter than the user, you're one of the many reasons your company is going out of business.
I also hate that "feature".
The problem is when the warning is a "stop" and it doesn't have an override "I know what I'm doing".
I don't know how I feel about it, but I feel like this has happened in multiple places now: The dominant option is losing ground to competitors, not because they got better, but because the dominant option got worse. I've similarly argued that the Linux Desktop is now at least as good as Windows (and possibly MacOS), not because our UIs suddenly got more friendly (although they have improved), but because Microsoft shipped the Windows 8 ("who needs the start menu?") and 10 ("we'll merge the old and new control panels any day^wyear^wdecade now") interfaces, so the bar is so much lower. I don't know that this is progress, but it's great if you want FOSS to win. Likewise, it sucks that Google is getting worse, but hey, at least now there's less reason not to use DDG...
Who else here doesn't use !g?
It's been a long time since I used !g for anything. I did for awhile as an alternate search, but eventually it stopped being helpful -- if I didn't find any good results in DDG, then the Google results didn't help either. At this point it's probably been a couple years since I did a !g for anything.
If DDG has an flag to use location info for search relevance, I'd do that instead.
I do regularly use other Google search services, though. In particular, Google Books.