There’s a talk by Rob Pike where he mentions that it would have been difficult for code using map, filter, etc. to be as fast as the equivalent code using a for

There’s a talk by Rob Pike where he mentions that it would have been difficult for code using map, filter, etc. to be as fast as the equivalent code using a for loop without a sufficiently smart compiler. So I think the motivation was more implementation simplicity . But if they had tried to add zero cost iterators it probably would have leaked complexity into the language too.