I think you mean a 1 in 4 chance of getting him out. A .666 hitter gets out 1 out of 3 times.
I'm a guy that walks more than most as a pitcher, and I can tell you the math is much more complicated than that. In my mind, it looks more like this...
Hitting his pitch he hits 800
Hitting my pitch he hits 400
Oops, it's 2-1, I'm still going to throw my pitch, but my pitch that's a strike 70% of the time, not my good pitch that's a strike 10% of the time that I throw when he has 2 strikes.
Oh crap, it's 3-1 and there are already two on and there's a really good hitter behind him, so I have to throw basically a meatball.
I don't like to be in that last scenario, so sometimes I'll still throw that borderline, 25% of the time strike call pitch to try and get him to reach because I'd rather face the next guy with a clean count and one extra runner on, than have to throw meat to this guy. I'm not saying I'm always right, but that's my thinking.
Yes, a walk is 100% indefensible. There is also still a chance that a batter will swing at a ball too though. I'm not saying I'm a world class pitcher by any means, but I'd put my opponents OBP up against most in my class, and I do it with those walks. It can make it hard when I join a new team that's used to having a meatball pitcher and they think any walks is a bad thing. Also, I'm trying to remember to add in the, my defense is losing focus because they're standing out there while I throw 5 pitches to every batter variable. Because of that I've started throwing more first pitch strikes.