And there are car owners who wish their car could fly, or go across a lake (without a bridge) and there were (are?) even companies that tried to give those things to those people but they were always compromises and expensive as heck. So most people accept their cars don't fly or go acrosss water, and if they want those things (and can afford them) they buy planes and boats.
The fact that some people want their iPads to be Macs, or their Macs to be iPads, and they want it for free (a lot of people always want it for cheap here), doesn't mean Apple has to accommodate them. And you keep bringing up marketing as if it means something.
You can say an iPad is just a bigger iPhone, but to me it's more and I have no problem that Apple designs operating systems specific to both. why does that bother you so much?
I don't know, and neither does anyone here, why Apple doesn't accommodate those that want to dock their iPads and have Mac OS available to them. They 'apple is evil' crowd will say its evil apple forcing you to buy two devices, but I do believe Apple always has the user in mind and they do not sacrifice quality of an experience for a gimmick. And Apple engineers are smart. So I believe the MacOS experience is compromised when running on existing iPads. I would not be surprised to learn it's a thermal issue. Macs run hot, even an Air, but the heat is separated from the screen by at least a keyboard and air. I don't know what the impact on a screen's life would be having the thermal heat pressed right to it. My guess is OLED would not do well with that. Or perhaps there is another technical aspect. But the fact remains is Apple has a history of improving devices even if it means the cannibalize another product line, the iPhone ate the iPod for example. The MacBooks have won over their desktops. Given how many more iPads that they sell, my guess is if they could make it a Mac too, they would. If nothing else it would dive more screen sales.
But I have experience in manufacturing and product design and I know what a user often this is easy, just isn't.