Once again that is your opinion for you, but that just isn't true for everyone. So, you've given your opinion and I've given mine, we disagree. I think the size has made a big difference in the way I use the device. I never connected the larger iPad to the audio system in my car, but I do the iPad Mini which is even controls the music app and Pandora for long trips. I find the size makes is more conducive to take to meeting and when have to take quick trips to various offices. I just never bothered with the larger one. Which I do use a great deal at home because it just seems to work better there. So, one is for work and use in the car and the other is for use at home and because it has a bigger display which is better that adds to the pleasure. Not to mention other family members using it.
You don't have to see a point in why people are buying both. But to say its ridiculous, waste of money and ludicrous just shows how shortsighted some people (YOU) can be. I have ZERO financial worries or concerns. What people do with their money shouldn't be a concern of yours. You've decided what is best for you, but that clearly doesn't apply to everyone.