AEA AGMA SM is better positioned to answer things from a union standpoint with regard to specifics, but the short version is, between union costs, filming costs, getting the rights, finding a distributor for release, marketing costs, etc., the relatively few people who actually purchase the DVD don't constitute enough revenue to create a good profit margin for commercially released versions of such pro shots (obviously there are exceptions, for example the Les Mis anniversary shoots, but do you see large markets for releases of, say, Merrily We Roll Along or The Drowsy Chaperone?).
The bottom line, sad to say, is money. And the problem with filming and releasing live versions of musicals commercially is that it's simply not lucrative. Only the biggest shows (like a Les Mis, like a Phantom, like a Rent, like a Jesus Christ Superstar) are ever going to generate a profit if they're filmed and released. For it to work for those involved, and to keep going at a more steady rate, people need to buy these like they buy Hollywood blockbusters, and they just don't.
As for anything newer, like online streaming (through such services as iTunes, Amazon, Hulu, etc.) or made-to-order DVDs, both of which sound like safe bets for even minor profitability, the technology is too new for theater as a whole to catch up with, and especially so with regard to unions.
Speaking as a producer, we would love nothing more than to be able to preserve musicals like this on a regular basis. It's intelligent not just in terms of preservation, but in terms of revenue, as seen from the upward spike in ticket sales that long-running Broadway shows like Chicago and The Phantom of the Opera received when their respective standard feature motion picture versions were released (i.e., it helped the profits rather than hindered them, the latter of which has been a complaint that other producers have used to justify their avoidance of producing filmed theater). But first, it has to make fiscal sense. And right now, it doesn't.
Formerly gvendo2005
Broadway Legend
joined: 5/1/05
Blocked: After Eight, suestorm, david_fick, emlodik, lovebwy, Dave28282, joevitus, BorisTomashevsky, Seb28