Why do most programming languages only return a single value from a function? Wouldn't support for more "natural" outputs be better?

The C language can be used for mathematical operations, ranging from additions and subtractions to square roots and cube roots, along with other polynomial powers that can be created through C ...

However I am pretty sure this is poor programming practice: aren't you supposed to limit the number of parameters to a function call to be at most something like 4?