There are other threads about it. Plus, it happened to me - so the most likely explanation from my end is that it happens in 100% of cases ;).
http://www.google.com/search?q=mail+stuck+in+outbox+gmail
A single quora answer alone has 20k views. Do you think that's a normal number of views on a quora answer? How many views do you think that quora answer should have for you to think it's a problem? 200k? 2m? 20m? 200m? 2b?
(A single quora answer does not represent everyone who has a problem. Maybe 0.01% of people with a specific problem will end up reading a specific quora answer. So I think that 20k represents 200 million users, or more than 10% of Gmail's userbase. While we're just throwing around made up numbers. Maybe it's 100% of installed gmail for android apps with that problem. (Since not every gmail user uses android, uses the android app, and uses it to send mail.)
Anyway I think up to 100% of the android app users could be affected.
Still, you answered the question: perhaps the development team doesn't feel that 20,000 reports is a priority. Maybe the salt and pepper manufacturer doesn't care that every one of their pepper shakers doesn't let peppers out. 20,000 complaints just don't matter.
Important people use iPhone anyway.