n. Often adduced as the reason or motivation for expending effort toward a seemingly useless goal, the point being that the accomplished goal is a hack. For example, MacLISP had features for reading and printing Roman numerals, which were installed purely for hack value.
See display hack for one method of computing hack value, but this cannot really be explained. As a great artist once said of jazz:
"If you hafta ask, you ain't never goin' to find out."