I mean ... it's all pure calculation. I used to work for the german label "Turbine" as a product tester (latest project was the Knight Rider Anniversary box with the first time worldwide uncut episodes and restored all original music on the show) and so I do have a little insight there. The four season set was sold for 200€, and that was already the lowest price we could take, unless we wanted to lose money. If we did Dallas with 13 seasons, the complete Set would have cost more than 700$ for consumers.
A bluray glasmaster, which is needed for pressing/mass production of each bluray costs around 1000$ per unit. If you want to put the whole show on blurays, you need about 85 of those glasmasters (if you wanna have decent kompression and go with 4 episodes per disc).
That comes to 85.000$ already. Then you need to pay the AACS copy protection fee per disc, which is another high factor and adds a huge amount to that price.
Then someone has to do the mastering, noone works for free. Package design and material. Then shipping costs.
You will have to sell hundreds of thousands of complete Box sets to make a profit out of such a massive episode count show.
And if you are a smaller label like Turbine Germany and want to licence the show to publish it yourself, it's even way more expensive, as you have to pay like 30.000 per season just for the licence and then on top of that about 30% of the profit to the licence holder (Warner in that case), so forget about that as well, not going to happen.
You won't find enough buyers worldwide to make this project profitable for Warner or any other smaller label, unless buyers are willing to pay 500+$ per complete set.
From a pure business standpoint Dallas on Bluray is just not-going-to-happen, and that's that. Period.