Sure it takes more time. You have to import your files in to LR or whatever convertor you use. You have to select all of them and apply your formulas and do a batch process. Then you have to create a folder separate from your original, then tie your computer up for however long it takes to process these images. An hour or so later you come back and then you can send them to your client. It is all time and if it isn't necessary for someone selling their pictures why make the extra work? No need in it for that person.
This would be a valid argument if you are using your computer 24/7 and therefore the extra time the computer was "tied up" was an unrecoverable loss of your time or you feel the need to sit there and watch it work. But that is not likely the case. While the computer is doing the imports and batch processing that time can be used for other things.
How about this, I want to go to CR and debate RAW files and my computer is slow and sluggish because it is tied up converting RAW files because I am on a deadline to get the pictures out. Any task is easier if you can finish it one sitting and don't have to go do something and come back to it. Or maybe I want to download the latest movie and my computer is bogged down, I might not even be able to play Pants vs Zombies, what do I do then?
Extra work is extra work, it wouldn't be a problem if I worked for the federal government, from my experience they seem to thrive on meaningless extra work. Those of us that have to be productive do not do extra work unless we have to.
A little stubborn and defensive? I already conceded that if you are already using your computer 24/7 then there could be some loss of productivity, I just don't think that's very likely for most... but sure if you need to play games or waste time getting defensive on CR then you have a point. Of course, if you're doing those things then I don't accept you're on a tight deadline to get images out to your client.
Anyone can dream up hypothetical situations where the "computer time" to batch process is a loss of productivity but it's just not broadly applicable. Even awin's example of a 2000 image library from a wedding shoot is a weak case because you would not likely have a 24-hour turn around on a wedding so the batch could be run overnight. A commercial shoot with a 24-hour turnaround would not involve thousands of images, maybe a few hundred and in those cases you'd likely be editing anyway so need RAW which Awin stated himself.