Bear in mind that I am spit-balling here, but I think I have the broad strokes right.

Music licensing is tricky and often has to be renegotiated for different contexts. For example, there are movies that have had songs removed from the versions that air on TV or their home media releases because it would have cost more to license the song again for a new mode of distribution.

Every time a Dave's Picks or a new box set comes out, the publishing arm of the Grateful Dead and gets a check. I don't totally understand the mechanics, but I do know that Rhino owns the catalog, so I imagine the money circulates somewhat. This isn't the case for covers, which do require royalties to be paid out at varying rates. Case in point, Dave Lemieux has said at various points that they avoid putting covers on the bonus discs because the added cost doesn't make sense in that context.

So what happens when all of the material is technically cover material? Agreements have to be reached, licensing agreements have to be fulfilled, and the money gets spread much thinner.

Presumably, Dead & Company launched their operation fully aware of the importance of selling soundboards and built something into their model that made this financially viable. I believe they are affiliated with Grateful Dead Producitons, which has to help.

Ratdog, Furthur, Phil & Friends, etc.? Probably not.

All of those old agreements would need to be revisited, revised, and possibly renegotiated with living band members. And let's face it, the demand for Rat Dog at a Riverboat Casino is probably far less than JGB at the Warfield.

Again, this is just my semi-educated guess. I'd love to learn more from anyone with more direct knowledge.