While I agree with other posters that this has been done to death, I don't think there is any reason to be rude. Since I've answered the why I'll give you a link to my own post explaining why I think the retina display simply wasn't possible in the form factor -
https://forums.macrumors.com/threads/1513636/
With that said, technology advances on and the computing power in the current fullsize iPad was out of reach for the original iPad so a retina iPad mini is likely at some point. My personal thought is that Apple will rationalise their product line shortly and drop the iPad 2 when they release the iPad 5. They'll likely do a speed bump on the mini while they test out new energy saving technologies on the full size example since the new one looks like it will be a bit smaller and they'll use retina and 128GB availability as the distinguishing factors between the full size and mini. Putting retina in the mini when it is already selling like hot cakes would be a financial mistake since it will dramatically reduce the sales of the more expensive product so keeping a little clear water between the two makes sense but the iPad 2's continued existence doesn't although that may move into the education or business only store and stop being actively sold to consumers as they run their supplies down.
I think Apple made a sensible call - they could release a smaller device into the market and still make a decent profit. It has some advantages and disadvantages but it is still in every way an iPad. I remember the iPod mini coming out when I had the 40GB fatty iPod and I thought it was ridiculously small capacity at 4GB but my wife wanted one and she loved it. Don't underestimate the cost saving versus some loss of utility. I have an iPad mini and so does my wife and we love them even though we have iPhones too and the lack of retina display isn't an issue for us since the lightness and battery life trump that and it is certainly a step up from my original iPad. Gaming on the mini is much better than on the full size.