Why you screen who you invite to training

This training class is getting more and more hillarious.

Yesterday it was very clear (at least to me) that the following things were true:
1) Only 2 of the people in the class were technically competent to operate the softwrae
2) Only 2 of the people in the class understood why we purchased said software
3) One 1 person in the class has an idea of how to use this in the larger enterprise setting, and he's the instructor and doesn't know the specifics of the contract we had in mind.

I leave myself out of the 3rd category because I really fall into this 4th item
4) At least one person (that's me) has no freaking clue why they're supposed to be there.

Anyway, while I sit and work through the exercises in the training manual (which are actually quite fun), the others sit and argue back and forth about why we need this and who's going to use it, and why are we doing this when we already have packages X and Y that do sort of similar things and how is it all going to integrate, and on and on.

And I chuckle to myself and wonder the following:
1) Shouldn't this have been discussed before the purchase was made?
2) Since it wasn't, could we just go on with the training, uninterrupted, and let you all hash this out later, cause it's a really boring conversation.