I think you underestimate the amount of work that's required when "proofreading", you need another translator that could have done the work themselves. And it's

I think you underestimate the amount of work that's required when "proofreading", you need another translator that could have done the work themselves. And it's not like you can just exchange a few words here and there and consider it done. If a human has to make corrections they'll likely rewrite the entire sentence and then the advantage of machine-assisted translation is pretty much gone. Overall you'll save time but the amount of time saved is probably less than what we think.