I agree and share your concern, Tom. I check my hubs time after times for mistakes of any kind, I might have overlooked and I am not proud to admit it, but I have found, plenty.
The problem, in my instance, is that regardless of having a degree in English language, that is not my native language and moreover, I haven't practiced it much, especially in written, since the times of school.
Please don't take it as an excuse, but rather as an explanation, of why the above mentioned mistakes happen. I joined hubpages, among other reasons also to learn more and perfect my writing style. I still find the idea of having the hubs reviewed by edtiors really good. That would maybe result in better quality hubs.