Why weren't some of my favorite songs from the Beatles available in The Beatles: Rock Band?

To give you some insight into the song selection process for the on-disc songs, Here is a portion of an interview between Harmonix CFO and Co-Founder, Alex Rigopulos, and Giles Martin, Creative Producer and Music Supervisor for The Beatles: Rock Band. (You can read the full interview here: http://www.thebeatlesrockband.com/behindthescenes).

Giles: And we also added and crossed out songs with just thinking of different scenarios for the game itself. I mean, we have Cavern Club, Shea Stadium, Budokan, and we wanted to make sure we represented those eras in the right way. There were so many different forces working to choose this song list. I'm very happy with what we've ended up with. I think it's a good representation of what [The Beatles] have done. But, you know more to come I suppose.

Alex: It's an incredible list of 45 songs, but one of the opportunities of downloadable content is that [there is] great music that didn't make the initial cut, or wasn't appropriate for game disc for one reason or another, and we will have an opportunity to deliver that music in interactive form to the players of the game subsequent to the disc's release.

Don't forget that we have several more albums available for The Beatles: Rock Band as DLC: Abbey Road, Sgt. Pepper's Lonely Hearts Club Band, and Rubber Soul.