It's a one type, not a zero type - the function does return and it always returns the same thing. It makes this kind of function more normal and regular - you c

It's a one type, not a zero type - the function does return and it always returns the same thing. It makes this kind of function more normal and regular - you can say that functions always return 1 value, and then it means you don't have to special-case void functions (which is a problem you have to work around in e.g. C++ templating), you can do things like put the return value of the function in a variable and then use it for something since it's just a normal value (which matters if you want to write e.g. a generic compose function that runs a bunch of functions in, IDK, a database transaction or something).