I'm not an expert, but apparently transport accounts for only 11% of carbon emissions for food [1], and I suppose it's likely similar for beer. To me this suggests factors affecting production are far more important.
Currying support is orthogonal to how function arguments work. Some languages (e.g. OCaml according to this question[1]) combine named parameters with currying, allowing partial application with any of the function's arguments.
I think this is the mistake a lot of people make: they form an intuition of monads after seeing lots of examples of them, and then they try to communicate that intuition without just saying "here are lots of examples of monads".
Just to clarify: there are lots of numbers that aren't real numbers (for example, imaginary numbers). Intuitively the real numbers are all the points along the number line, including rationals and irrationals (such as root 2, pi, or e). There are lots of other comments in this thread that give a good explanation of how that works formally.
If the students haven't yet encountered complex numbers, infinitesimals, infinities etc. then it's perfectly reasonable to say that all numbers are assumed to be real (as follows strictly from the definition in the book).