Because consoles did not browse web, or check email. Consoles did not replace PC, tablets do. There's a huge difference.
Best options don't necessarily come with bigger packages. You need to realize that PC's are much harder to use than tablets.
I do believe that the consoles of today (predating the iOS) can browse the web and check email, they can even play BDs! Perhaps you never entered into the discussion a decade or decade and a half ago, but then consoles *were* going to replace PCs - it was a done deal - according to many many enthusiasts.
It never happened (obviously) but consoles were among other things, simpler to use and cheaper than computers.
For years people have been able to receive email and to an extent browse the internet on their cell phones and that didn't create a "post-PC" era. It wasn't even when Bill Gates (according to you) coined the phrase. No, it was when Steve Jobs claimed it and many many people believed him.
I could have mentioned that in 2006 I saw far more people spending time on their cell phones than ever on their computers, yet I wasn't convinced that we were in a "post-PC" era than any more than now.
Also while you are of course correct that iOS devices are easier to use than PCs, we both know they are way more limited. That limitation is in no small part what makes them simple to use.
So while they are limited and easy to use they are appealing as such, but when they get more features and more power, one has to consider a normal PC as a better choice. Thus the tablets (at least according to Apple) have to be simple and easy to use - and limited.
But when you have a more capable tablet, one that rivals the Mac OS in features, then why a tablet .. and is there then any particular difference between a tablet and a PC? Look at what MS is offering in Windows 8, where they are going to blur the line completely between a tablet and a PC, by offering the very same OS on both.
Sure tablets are and will be convenient devices, but essentially they're just very portable PCs with a touch-screen. That's all the magic.
