why don't they? we spent half of our time in aikido attacking, why don't we be proficient with attacks? if we are not, then aren't we wasting half of our time?
I was taught, and it seems borne out in my experience, that if you don't take the role of uke seriously you are missing more
than half of the training.
As I reflect on this over the years, I continue to find it true on many levels.
The techniques we learn as uke are probably more useful and more practical in many situations than, and often serve as a bridge to the more glorified techniques from nage's side of the practice, and are most definitely part of aikido.
Whether "attack" is a part of aikido is a whole other discussion.