Except, most UK undergraduates in mathematics, engineering and the sciences now do a 4-year first degree, albeit a taught masters.
If you meet someone styled MEng, MMath, MSci or MChem, that's generally what they've got. Note they generally do not have e.g. BEng MEng or BSc MEng: the fourth year has an extended project/thesis element but is not a separate degree.
It's all very nice to have a masters as your first degree, but you can't really escape the fact that university expansion and the eroding standards of A-levels, together with the technological demands of the modern world, mean it's very hard for three years of higher education in the sciences to be enough.
The 3 years we do in the UK generally contains the same amount of the chosen subject as the 4 year degrees in America do as far as I can see. The main difference is that we only do our subject, whereas students in America often do lots of extra and quite different modules. I think there is some merit to that system.
Also, I wouldn't say that most undergrads in STEM do 4 year masters degrees in the UK. I think a fair few do, but going on what I've seen from friends, and what I saw when I was applying for my CS degree 4 years ago, which I'm coming to the end of now, it can often be difficult to find places that do the 4 year masters. For CS, there were probably fewer than 10 places in the country that did MEng. This is just my experience though, it might be changing, and I'm a few years out of date.
If you meet someone styled MEng, MMath, MSci or MChem, that's generally what they've got. Note they generally do not have e.g. BEng MEng or BSc MEng: the fourth year has an extended project/thesis element but is not a separate degree.
It's all very nice to have a masters as your first degree, but you can't really escape the fact that university expansion and the eroding standards of A-levels, together with the technological demands of the modern world, mean it's very hard for three years of higher education in the sciences to be enough.