For what it's worth...I do the same thing. I know that I make grammatical errors frequently because my brain and my fingers don't work at the same speed. And sometimes, even when I re-read it looking for grammar, my brain starts working on revision of wording/emphasis more than grammar. I almost feel like my brain just doesn't care as much about grammar as it does, as you say, about the intrinsic value of what I'm saying. So, you're not alone. I share your views about it not always being a matter of laziness. I'd say it's more about priorities.