I really don't need instant access to tons of movies, but my kids watch a lot of the same ones over and over, so I keep those on Plex, rather than paying for Disney plus or whatever.
After ripping I usually increase the crf a little to reduce the file size to host on plex. Movies that we are watching a lot live on Plex, but if we stop watching something, or it seems like a one-time thing, then they can be removed from the library.
The burned DVDs are really more of a personal archive. Those movies could get added back to Plex someday. I don't need all of Lost or Breaking Bad on my Plex server, because I've recently watched them, so they'll live in the DVD drawer for a few years.
But otherwise, I don't see any real plus. Unless you have such a large collection that the search/recommend features are useful. You still have to take the DVD out, put it in the computer, run some program, etc.
I honestly don't know, because I rip all my content and play it on Plex. :)
This could be the answer and once you're ripping content anyway, Plex is a decent way to stream it to whichever devices.