Steve is right, commercial is the word. The problem is most people who work in DVD industry know about commerce but little about film. It is easy to sell new product as expected sales are often related to theatrical performance. The bigger companies who have the rights of films going back a5t least 70 years are having probably so much relative success with their new product that they are paying little consideration to their back catalogue. I know that some of the studios have been perplexed as to why they have failed to do as well as other companies in selling classic titles on DVD. And I am not referring to films made before 1960. Even classics from the 80's failed to garner the interest they expected.
At first, new films had a load of extras readily available ('deleted scenes' etc) and people on hand from the cast and crew that were readily available to record their commentaries, after all there was a vested interest (i.e. self promotion to aid their career in the future) if not contractual obligation to do so. Also it is in the interests of actors and directors who are set to gain residual payments from the DVD sales of their films. The studios applied the same approach when it came to their back catalogue. Naturally, even for actors and directors od films going back only twenty years, promoting their old work would in no way have the same returns and many were not interested in helping the studios make more money off them with little financial benefits for themselves. It took smaller companies like Anchor Bay, who took a greater interest in the medium of film and the merits of the work they aimed to release, as well as financially rewarding those who participated, to persuade people like Alex Cox, Val Guest, Roy Ward Baker, Nigel Kneale etc that their contributions would be more worthwhile. In turn, the attention paid made the end product of greater interest and quality, as well as putting a greater retail value on each title.
Most classic British films are now in the hands of two companies. Carlton own films previously produced by Rank (inc. Gaumont-British and Two Cities), Romulus Films, Gainsborough Pictures and London Films. Canal+ Image Ltd own the rights to films produced by Ealing Studios, British Intl'l Pictures, Associated British and British Lion. Carlton have released a fair chunk of the British films they hold and have begun paying some attention to some of their films. The African Queen comes with a Jack cardiff audio commentary and Carlton have specially made half hour docs on Genevieve, Black Narcissus (though no sight of the film in the UK), The Life and Death of Colonel Blimp, Brief Encounter, A Matter of Life and Death. The Red Shoes, A Tale of Two Cities, The Importance of Being Earnest (1951), In Which We Serve, Oliver Twist, The Battle of the River Plate, the Doctor series and the early work of Alfred Hitchcock. Canal+ Image release through Warner here in the UK. So far they have released only a fraction of films own as far as classic British film is concerned, and none have come with any extras other than a few postcards. Those that have been released have mostly come in boxsets (the three different Ealing Studios boxsets). A company called DD video also begun releasing some old British films on DVD but none came with any extras until recently when they took on the early Hammer films which had previously been released by Anchor Bay in the US, sensibly acquiring all the extras that came with them (inc. many audio commentaries). Hopefully they will go down this line themselves and produce special editions of their own.
Of the films you list I know of one title that is available now. Kino International have a DVD of Wings of the Morning that comes with another film, St Martin's Lane (starring Charles Laughton, Vivien Leigh and Rex Harrison) - go to
http://www.kino.com/video/item.php?product_id=702. Jassy and Sixty Glorious Years are available on VHS on DD video, maybe they will release them on DVD in time. Considering the number of films that have been released on video, I am sure many will come out in time on DVD. I just hope that opportunities are taken to record additional features such as audio commentaries are taken sooner rather than later.