Maybe you were leaving it for too long before drinking it...

That said, I had a colleague who was mad keen on getting absolutely the perfect traditional milk. This meant the proper kind of high-speed machine had to do the shaking. But it also, apparently, meant using old milk.

He would actually ask servers whether the milk fresh, and walk out if they said "yes".

All of my anecdotes on the matter are EU (possibly all BE/FR, not sure) vs UK, so it's possible UK and US pasteurised milk tastes different (I've had many lattes in America but can't remember ever drinking straight milk or over cereal there..)

Or it's possible my sample size was too small. Would be curious to know how many people feel which way, but somehow doubt there's any good data sets for that!