Jpeg is a lossy format, ..., it is not an archiving, storage or intermediate format where further work or more advanced processing from newer processes is used. Just look at Lightroom Process Versions over the years, 2003-2010-2012 dramatic differences in processing capabilities to lossless images, totally lost on jpegs.
This is why I prefer JPEG's ... it means I don't keep on reprocessing my (ancient) photos of bushbucks and caracals, but have to go out into the field and take new pictures.
Bob: "Look, a fish eagle! Hey, aren't you going to take a picture?"
Sella: "Nah, I took a picture of a fish eagle in 2004 in RAW format ... I just keep reprocessing that everytime Adobe upgrades Lightroom."