Isn't modern technology grand? See also pasteurization, canning, pickling, and many many other technologies that help food last longer. Why should people care what something is "supposed to" do? Many kinds of food are "supposed to" spoil quickly, but we've gone to great lengths to overcome that.

(For clarity in case there is a nomenclature difference here, UHT milk is shelf-stable liquid milk that's entirely equivalent to any milk but lasts much longer before expiring. That's separate from things like evaporated milk or powdered milk, which are also substitutes for milk but not directly equivalent.)

UHT milk does not taste like fresh milk. Sure it is safe for months, but it isn't good for months.

I once was at a farmers place - when they were done milking the cows in the morning they brought milk in from the tank for breakfast - ever since then I can't drink store bought milk as fresh milk tastes so much better. (the milk was also unpasteurized, I believe fresh was the key to taste but I'm not sure)

I'd argue the difference between UHT milk and standard pasteurized milk is much smaller than the difference between either and fresh milk, and most people don't buy fresh milk (or want to).

But in any case, it's good that multiple options exist.

Sure, but I mostly need milk for coffee, and sometimes for stuff like puddings, so a liter of milk either lasts a week, or I just need two liters right now for a unplanned batch of pudding/milk rice/etc. UHT is good enough for both. I don't drink milk directly.

UHT pasteurised milk. The one I have at home now has an expiration date in late june.