Why doesn’t diesel come?

Hello, where is the problem of bringing an UP! or cross-up! as diesel? All the most impossible and absurd models for any niches are now thrown on the market. But an UP diesel does not come, although not so few diesels were sold by the Fox. What reasons does that have? – Supposedly the UP diesel is not worth for the customer. But can not be an argument, as this would apply to over 50% of all car models. – Many drivers drive at least polo or should go to the grei Who says that? Shouldn’t the decision be left to the customer. There should also be people who drive diesel on the basis of better torque and not for economic reasons. – Are there any arrangements to leave this niche to the Fiat Panda? I don’t understand. Greetings