It looks like you're right about achievements (Fallout 3 has them, but I didn't remember them in Oblivion at all) and Kinect, though adding support for both it and Move would surely take quite a while -- something PC gamers wouldn't like, even if console gamers begged for it.
It also looks like the release date was a wrong example to bring up. However, since it couldn't be added to the PC version pre-release, it would probably take a bit of time to create (and resources), both of which could be spent on developing another game or creating DLC. That's just more time and money put into making the PC version better, even if it isn't what sells the series to gamers. Given that console gamers are the biggest market for Bethesda right now, something should be done to make the game more enjoyable for them. No, simply making it for consoles isn't enough. The PC version gets many things that the console version doesn't, and the excuse that it's justifiable because the PC is capable of those features isn't a good enough for me.
It's better for them to appeal to their largest market, which would mean console-exclusive DLC or other enhanced features. You can say all you want about that being unfair or selfish, but if it's consoles that earn Bethesda more money than PCs, more development time and resources should be poured into features for consoles.
I believe Oblivion on Steam had achievements, don't know if that was patched into the console versions. As for kinect, it's fully supported, both officially and unofficially, on PC - I think it's a stupid idea not because of platform issues, but because *it's a stupid idea*.
A DX11 patch certainly could happen post-release, it'd be harder than writing it at first, but there are no limitations on what a patch can do, it edits files, that's all. If they have their level designers and quest authors writing my DX11 patch, I don't want it! Graphics programmers, on the other hand, I'd love to have working on it. The two needn't interfere at all.
It's better for them to appeal to their entire market - arbitrary console-exclusive DLC is entirely against that. There's absolutely no reason to limit it, other than to satisfy your jealously.
I would assume that when Skyrim is done, they're going to start work on whatever they're doing next. This game will almost certainly have most, if not all, of the features we silly PC gamers want, simply because it'll be released in, probably, half a decade's time. They're writing it anyway. Being able to release it as a Skyrim patch would require a different approach, and a little more work to package it, but it's far from doing it entirely for PC gamers playing skyrim - they're going to do it anyway. It'd be awesome if they decided to patch it in later, but that's really a decision they have to make now, and stick to it, otherwise it'd be too much work to justify.
I'm not saying anything about "unfair" at all - I do think that you wanting exclusive content because your platform can't run modern technology is selfish, however.