I think what makes reduce less popular is that it takes two lambdas:

- a slightly awkward one that takes a partial result and the next value to produce a new partial result

- one that maps the final partial result to the result

Also, in many languages, when reading the code, you have to skip initialization of the partial result, read the lambda, and then jump back to make sense of the initial values

I think something like awk’s syntax, with BEGIN and END blocks would improve on that. Example of a first go at such syntax (needs work):

  Items.BEGIN
    min = ∞
    max = -∞
    sum = 0
    n = 0
  ITER
    min = Min(min,_)
    max = Max(max,_)
    n += 1
    sum += _
  RETURN
    average = sum / n
    (min, max, average)

- items in the partial results have names, making them easier to understand

- result also is easier to understand

Price paid is wordiness, and you cannot simply write a function name for either of the lambdas.

However, I think the latter only is useful in case the partial result is the final result. There, you can keep

  sum = items.reduce(0,+)