Can someone please explain me the utility of TIFF files these agencies offer?

I'm not a contributor..but after a research i think it works something like this: Contributors upload in JPG and agencies convert it in TIFF. (correct me if I'm wrong)

If i'm right: we all know that TIFF is designed to save-export and not lose much quality as JPG do.

So if you made a TIFF from JPG you'll get the same quality, only with greater size in MB. Therefore have no sense!

I leave the word to the experts!
Thanks in advance.