Dragnet is problematic. The first 100 shows are PD. Universal neglected to renew the copyrights on them as they are filmed versions of the radio show. The next 100 are copyrighted and then of the last 71, some are, some aren't. Not sure of the exact breakdown. For whatever reason, no one seems at all interested in the property.
What I have always been told on message boards about Dragnet 5X is that the films were locked away in the Universal Vaults in the 60s, roughly around the time Dragnet 6X began, and have remained there since. And, the major problem with Dragnet 5X coming to DVD is that there are no readily available digital or even videotape masters to work from, since the show was never syndicated after the mid-60s. So, bringing Dragnet 5X to DVD would involve making new digital masters from the original film elements, which would probably cost more than Universal, Shout, or whatever company releasing it would make on the sets. Sort of like what you described the Hec Ramsay situation being.
At least, that's what I've always heard from random people on the internet.
I don't see where Public Domain would be as big an issue, since only around 30 episodes have ever popped up on PD releases, and they're mostly in horrible condition. Sure, cheap DVDs have flooded the market, but no season sets.
Edited by The Obsolete Man, August 30 2013 - 09:58 AM.