> 1) why wasn't AGPL used for GPLv3?
I don't know the actual reason, but these are my opinions. First, I seem to remember at the time the GPLv3 was being worked on there was some push to include the language from the AGPL. I believe (though I could be mistaken -- it was a long time ago) that the wording in AGPL was considered to be a bit ambiguous. There was some worry that the definitions of "convey" and/or "propogate" (I think) were not on solid footing. Eventually all that got sorted out and without looking at the original text of the AGPL I can't recall off hand, but I think they changed the text for AGPLv3.
I think there was also some concern that perhaps AGPL was not the way to go. As you no doubt know, the intent of the GPL is to allow people to run software for any purpose. You can even modify the software and keep it to yourself. The need to include source code only ticks in when you distribute the binary -- so that the recipient has the same abilities you do (minus the ability to change the license). There definitely was some discussion at the time whether or not the AGPL's further restriction impinged on Freedom 0. I admit that I mostly ignored this conversation, so hopefully someone else will give you a better answer.
For myself, I've mostly moved over to the AGPL, but I still find some of the wording to be not as good as I would like (I won't bore you with the details). I feel that the GPL is a more secure and conservative license that has been tested quite thoroughly in the court. It was a difficult choice for me to decide which one I wanted to go with since I agree with the aims of the AGPL license, but don't quite trust it as a legal document to the extent that I do the GPL. I presume others feel the same way I do.
> 2) why should companies be able to keep proprietary version from being distributed?
Possibly my reasoning will appeal to you because it is bereft of moral qualifiers ;-) A license is a license. In most cases licenses give the recipient more freedoms than they would enjoy without the license (otherwise they wouldn't need a license -- in some complicated licenses you give up something in consideration for something else, but I won't get into that). The question is how much freedom should you give the recipient of your program?
I value software freedom. The software world is vastly better in my opinion since the concept of software freedom came into existence. I want to promote this kind of software and hope that it dominates for most software that I will come into contact with. Because of this I write free software and think hard about how to make pure free software businesses work (currently writing a game of all things...)
The most important part of free software from my personal perspective is the idea that there is an even playing field. To be honest, I don't even like the idea that the upstream author can change the license on you if they control the copyright. As a user, I want some continuity. I don't want to have a split where suddenly my local contributions have less value because I have to compete against software that I can no longer contribute to. This is not a moral choice in my personal view. It's purely selfish. I choose to use free software particularly because it stops a lot of shenanigans from the upstream producer.
On the other hand, as an author I also have needs. I choose to write free software. My downstream users do not necessarily have the same point of view that I do. I am not going to change the license (and encourage multiple copyright holders in my projects specifically to make it difficult to change the license). I don't want to compete against a downstream that has more options than I do. It's purely pragmatic.
Now, the question you will undoubtedly ask is, if I'm OK with this restriction, why am I not OK with the restrictions in these SaaS licences. Surely I understand that they are trying avoid competition with a downstream that has no obligation to contribute and can supply the same service with a higher efficiency (and therefore lower cost).
In truth, have a considerable amount of sympathy, but there are really two key issues. First, I do not want to use software with those restrictions. It's not like I wish fire and death to them, but I'm decidedly blaze about their existence. I'd rather collaborate with groups that treat me how I want to be treated, rather than groups that are not as bad as the other guys.
From an author's perspective, I understand their plight, but I actually don't think SaaS is a good way to sell services. It's rent seeking. As much as I appreciate the idea of a near O(1) (per user) complexity for cost structure, I think it results in services that... don't have much service if you get my idea. It devolves into the Googles of the world and I'm not actually that keen on it. I think there are better business models waiting to be discovered (but I'm busy with my crazy free software gaming business model and there is only so much crazy that even I can keep track of, so don't ask me to do it).
But, if they want to do it, I'm not picketing their offices. Neither am I picketing Microsoft, Adobe, or even Oracle. I don't like it, but I'm not king of the world. If you ask me to cheer them on? No thanks. If you ask me to say, "Surely this is better than not having it?" No thanks. It definitely isn't for me.