[davidmanze]

DNG is just a container format (a glorified TIFF) to store the RAW data.
It's not the most space efficient, but with the low cost of mass storage today, it's not really an issue.
If one wants to have universally accessible files (esp. in the future), DNG is better than any proprietary formats.
It also allows one to use older software versions without being forced to upgrade (as in David's case).

DNG loses everything a manufacturer stores besides what you call "RAW data". That makes DNG worse than most proprietary formats, also worse than CR2/3.

Most data stored by manufacturers are irrelevant if one shoots RAW. The only relevant manufacturers meta-data are correction matrices which is not needed anymore if the converter applies the correction (ML only).
Color settings and other parameters related to the jpeg engine are irrelevant if one shoots RAW and post-process anyway.
For years I converted my RAF Fuji files to DNG (using Iridient) which in turn I imported into LR.
For all intent and purposes, nothing useful was missing from  converting them to DNG.
Only recently I reverted to using RAF files when using C1 and now RawTherapee.

 D500 RAW files go from 21.8 Mbs to 38mbs when converted to DNG !! ...... why it gets bigger I don't know ??

  That's a considerable burden on disc space when for safety you keep two or three images.  You also lose the focus point Nikon kindly shows in the NEF image, pity,  all other useful exposure info remains.