Why tuples are not ranges?

[Mr.Bingo via Digitalmars-d-learn]

Seems like it would unify things quite a bit.

import std.typecons, std.range, std.array, std.algorithm, 
std.stdio;

void main()
{
        auto t = tuple(3,4,5,6);
        //auto t = [3,4,5,6];
        
        writeln(t.map!(a => 3*a).sum());
        
        
}