Look at this way. Say you have a total of 100, 500 or 1000 images within a folder or busted up into several folders. Do you process and convert all to tiff? or only a select amount? How do you keep track of all of it in deciding which you want to commit to tiff? Are you going to remember years down the road which of the 100's or 1000's were converted to tiff?
Or do you just backup copies to an external device or disc of all your raw files, maybe batch convert to DNG, and then only deal with the xmp edits of the files you're working with on your hard drive rather than keep track of all those select tiffs that will soon become a burden backing up and organizing.
All you're doing with raw is editing the preview generated between the raw converter and the video board. No one knows what's in any image file regardless of format without a video system. It's just that with raw you're working strictly off the preview which is a fast, efficient and less cumbersome way to work. Editing a large tiff requires a lot more extra steps, drop down menu's, processing power and waiting time the more complex the edits become.
With DNG the exported xmp based edits get embedded and carried with the file wherever it goes. With the original raw you have to deal with the sidecar xmp file and the only way to have it remain with the original raw is to keep both in the same folder. I've found when dragging and dropping copies of raw files out of Bridge onto the desktop, the xmp file doesn't always come along. So the xmp route has its limitations.
Other than that the gist of all of this is how many versions of a file does one want to keep track of and is it all that necessary.
