It's more about status than utility. As long as Go and Chess can maintain some sort of high status (as games or as historical points of interest) among the intelligent or ruling classes, they'll be remembered. Diseases seem to get status a different way. Humanity will probably remember the Plague for a long time still. Or if a biologically engineered supervirus was unleashed that killed a significant fraction of humanity over a short period of time, that too would be remembered. Quick mass death is the status currency of disease. If we ever get around to ending aging, probably one of the lowest-status problems on the to-do list, death by aging will be forgotten too.