[rando14775]

UHT to my taste also adds slightly bitter flavor. I grew up drinking fresh milk but my parents at some point switched to UHT and so did most people I know. I'm not sure if the middle ground longer-shelf-life type is actually more popular than UHT in Germany as someone here claims. UHT tasted bad to me (slightly off) back then, but now being used to it I have the opposite reaction and think something's wrong when I drink fresh milk. The difference in taste seems negligible when used as a cooking ingredient.

UHT (and longer-shelf life) milk became pretty popular in Germany during the late 90s I think. I'd speculate it's because it's much more convenient due to smaller fridges, as well as discounters (which are very popular) selling it for very cheap.

I will also agree with the other commenter that the type of heat treatment is the most obvious factor in how milk tastes, and that I've heard people from abroad comment on this. Though I've never had US milk so IDK.