I agree that having trained at drama school doesn't automatically give you more right to a role. It's whoever who can do the job best. However, training establishments exist for a reason and there would be little point ito them if producers ended up hiring the majority of casts "off the street" so to speak. Not everyone that goes to drama school will be an employable or a "good" actor but in terms of the well-renowned schools - there will be certain traits that will assist the trained actor to survive in the industry and be employable as a company member. I think in terms of the board, people want succesfully cast actors to have "earned it" in some way, and for many that includes having learnt your craft at drama school - which is now being promoted by Equity, Spotlight, etc as the best way forward to have an attempt at a succesful career in the performing arts (ever since rep has basically dissappeared).
I completely agree with all of this, and would always encourage people to train if they can (although would argue that drama schools sometimes miss talent and there are good reasons why some people don't train). I think there is an argument that the BBC has more of a responsibility to suggest to people watching these shows that training is good and that most roles don't just magically get handed to you, but require years and years of effort (and lack of work even after you get one good role!)
Interestingly, the word is that the frontrunners for 'Spring Awakening' are all around 16 (or even 15!) and mostly untrained. But I bet they will be given more support than the 17/18 year old 'IDA' contestants, who seem to be thrown to the wolves a bit and subject to some fairly cruel criticism.
I guess I was just making the point that it doesn't make sense to be angry at commercial theatre because it's money making rather than an artistic enterprise. To me, it would be better to direct anger elsewhere - eg at West End theatre owners who are demanding public money for upkeep of their buildings while packing even smaller playhouses with money making musicals, or at the government for failing to provide enough support for subsidised theatre so forcing producers to try to make money where they can, or at the BBC for failing to show the reality of life as a performer, and what it really means for these girls to be giving up their education at 17 or 18 and moving straight into trying to make a living as a performer.