The montage was probably added as an intro of sorts for the cassette version, although I'm not too clear on why it would be needed. Maybe viewers in the '80s weren't accustomed to just jumping into a movie like that. Still, I miss it now that I'm watching it without which is typical of me, I guess.
I'll probably do some digging to see if I can figure out the whys and wherefores of the siuation. If anyone out there happens to know the answer, I welcome the input.
That's it for me.
Update: I guess it didn't take very much digging after all! Beatles historian and DVD producer, Martin Lewis, answered this very question in a USA Today Talk Today column:
Roanoke, VA: Why wasn't the "I'll Cry Instead" intro included?
Martin Lewis: I'll Cry Instead was a 1982 creation that was devised as a marketing tool to help launch the theatrical reissue of the film by Universal Pictures. It was never a part of the original film, and the director Richard Lester detested it, as did I. I felt that my job as producer of the DVD edition of the film was to faithfully honor the work of the filmmakers as they intended it in 1964.
Ask and ye shall receive. Mystery solved, everyone can go home now.