It's possible that consumers declare the they don't prefer UHT milk when asked but actually buy UHT milk without realising. In Greece, UHT milk is often sold in similar packaging as fresh milk (i.e. in plastic bottles rather than cartons) and placed in the refrigerated section alongside fresh milk.

To confuse matters further, some UHT milk is sold separately, outside the fridge and in the typical carton packaging that one expects it. So it's very easy to be confused about what is UHT and what is fresh, just by looking at where a product is and how it's packaged.

Of course you'd think that the taste would give the milk away- but I find that if UHT milk is refrigerated, its "burned milk" taste is much reduced and can easily fool someone who only drinks a little milk at a time or mixed with other foods or drinks, e.g. in their coffee or cereals.