You said you understood that the Nexus 7 didn't have the feature you wanted when you bought it, and that it wasn't until later that you realized how much you missed that feature. Therefore, your disappointment should be directed at yourself, not the manufacturer. If you wanted the full tablet experience (whatever that means) in the 7" form factor, why didn't you buy a model that offers such a thing? Or why not complain about the other manufacturers of 7" tablets that have the video out feature, but whose tablet experience is lacking in other ways or whose price is much more expensive? Your remorse just seems to be misdirected.
You make it sound like it's simple and cheap to do the things you want, but that's not necessarily true. There's also engineering, programming, royalty, and support costs involved. The more features you add, the more complexity there is. The more complexity, the higher the cost, regardless of how cheap the actual part is.
Based on what the N7 sells for, I don't think Asus has a lot of margin to play with (it's a matter of percentages, not cents). A few cents (though I doubt it would just be a few cents) may not sound like much to you, but multiply that by tens of millions of units, and suddenly you're talking serious money. So to add such a feature just to appease a very small number of users wouldn't be make much business sense. They wouldn't sell significantly more, but their margins and profit would be reduced. That's not a good way to run a business, and I didn't even have to go to business school to figure that out.