Actually, you've missed the point quite spectacularly.
Sure, you can write a trivial* document like a PowerPoint-style presentation on a tablet.
However, I'd be pretty confident in saying that the main thing you did was select slides from various other presentations you and your colleagues have made and maybe adjust a couple of words on some of them.
That's not creation, that's roughly equivalent to editing a playlist. Certainly very useful and doubt skilled - it got you the contract after all - but not creation.
Even if you did write the slides from scratch, that's probably 200 words tops. Nothing.
You are not going to write a significant text document on something with no physical keyboard. An email? Sure. Hamlet? No way!
You are not going to draw or edit a significant image without a mouse or (better) brush/pen interface. Try drawing the Mona Lisa on your iPod Touch.
Yes, given enough time you probably could write out the likes of Hamlet on your iPod Touch. However, you're not going to try, are you?
Equally, would you be happy if you had to do your entire job on a iPod Touch? I mean all of it - no physical access to a PC/Mac at all, only WiFi? Do you think you could follow through on the contract using nothing but the iPod Touch?
I doubt it, you'll use something else that is more suited to creating the widget that you just sold.
That is what I mean by "It's for consumption, not creation".
Oh, and incidentally the Kindle Fire is an Android tablet and will almost certainly support the Android equivalent of whatever it was you were using to edit that presentation of yours, so your concept that "it's only iOS that are useful" is foolishness. Maybe when you bought your iOS device it was true, but it's not now.
*A good presentations is always trivial in terms of the actual quantity of written and drawn content. Put too much on a slide and nobody can read it, put in too many slides and everyone gets bored.