Government offices say: We want a copy of the autoresponse sent to such and such to verify it's sent out each time.
I see this as an extremely valid use as that is probably one of the biggest ways they can verify that it was indeed sent to the user so the user can't say "I was never sent that email or message etc."
I see this as a really good reason for being able to include multiple emails in the response email setup.
Now I do see this as overkill, and I'm not saying that it's a good idea that anyone would do this, but I do see it as a valid and useful reason TO do it. I wouldn't want to get all them response emails myself spammed to me every time someone fills out my form, but ...
Most likely they have these emails all tracked and sent to a specific email inbox and marking them as read right off the bat with a filter, and then they have a copy verifying at all times that the person in question did indeed get sent that response should any issues arise later that need to be confirmed.
Just my 10 cents
I can see other big businesses using something like this for verification purposes too.
