It's all about widening the demographic for the film as much as possible. With only few rare exceptions most people connected with creative endevours like films, TV programmes, books, plays, etc. are contractually obligated to do PR for the company that puts up the money to make it. I think it is quite evident that BC cares a lot about this film and wants it to do well and get Turing's story out to a wider audience. So he does as much publicity as his busy schedule will allow.
About it being repetative... that is the nature of the beast. It is only very pale in comparison but my hubby has gone on a number of publicity junkets for his books (TV, radio, newspaper, magazine interviews) and it was grinding and it wears you down, but if you care about your work, you do it regardless. It isn't easy flying all over the place and living away from familiar surroundings.
And he repeated the same info many times over because for each interview it is the first time they are asking you that question, so you do tend to stick with familiar phrases and topics to get your point across when you are tired and just really want to go home but still feel passionate about your work.
Some interviews are surprisingly pleasant and refreshing, others are downright embarrassing (one fellow hadn't read anything more than the dustjacket and asked completely inane questions) and yes, Dan was more comfortable talking with some interviewers than others (you can always tell when you see the videos).
That happens but it isn't really a big deal. It's part of the process.
I thought the Ellen show went well enough. He did look a bit nervous and a tad uncomfortable at times but nothing overtly so. It wasn't the best interview he has had and it was "fluffy" for the majority of it but it was the first time he has been on her show so it really isn't comparable to something like the Graham Norton show, is it?
If I had my druthers I would prefer BC to be on something like The Tavis Smiley Show on PBS. He's a great interviewer, serious and yet relaxing for him guests and he just does interviews (no comedy sketches or stand up routines). He usually has only two guests (and sometimes just a single guest) and they come out separately for their own segment for a one-on-one interview and that's it. But it is aired very late and so it doesn't get as huge as audience as something like one of the talk shows (Ellen or one of the late night comedian show - sorry I don't watch them so I don't know their names... Jimmie something).
Still I do hope someday BC will be on the Tavis Smiley show. It would be great.
-Val