So apart from the archival value (objections tend to be along the lines of "hey, we'll surely have time to fix the roof when we see the storm clouds")
real objections are that Adobe DNG converters in many cases either discards the part of raw data (many Pentax and Nikon raw files) or completely destroys it (Sigma .X3F raw files) and so on
, the key pluses are embedded previews and safely-embedded metadata, and how you can then take advantage of them in diverse workflows.
embedded previews only if you are using Adobe raw converters tools - other raw converters do not do this (or do not work w/ DNG at all or do not work with DNG fully and so on) so the value of that is zero for people who either do not use Adobe raw converters or use more than one raw converters according to the task... and out of LR using crowd most using the same LR for DAM and store images in LR database - so the point of having embedded previews and not having .xmp files is moot