Should Aikido incorporate strikes when surrounded in an alley? Most assuredly.
However, where we train, we concentrate on capturing an opponents center and then everything else (atemi, trow, hold), is just gravy.
I don't train in aikido because I ever hope or expect to use it in a fight. However, if I ever do find myself in a fight, I hope that somehow aikido will be useful to me.
That said, in the world of my other budo, that of the fighter pilot, we have an axiom that goes like this:
"you fight like you train."
In other words, when the time comes to fight, you will probably not think, but will do what you've trained to do. If you haven't trained to anticipate, look for, and exploit opportunities for atemi, I don't think you will do it in a fight. Too much thinking.
I only have 18 months practicing aikido, many years at that other "budo". I'm inclined to believe that what works on that battlefield is applicable to this one.
Besides, if O'Sensei said 90%, or 70%, who are we to argue?