Why is R5RS considered to be good

... when it includes ZERO functionality for a filter function or a fold function? Pathetic.

R6RS was a smart move. Too bad that ivory-tower academics felt it was too useful.

>>2

they can just be implementing as a simple recursive function in a portable way.

That is true, but considering how filter and fold are so commonly used, it would make sense for the interpreter to provide them to the programmer instead of having the programmer redefine basic procedures that should have been included in the language in the first place