Technically, it is not needed to ensure that NASA is funded. Congress and the current administration think it is needed, because they're stuck in the 1960s and think the space race is still a thing (meanwhile ignoring/underfunding crucial planetary and Earth climate sciences that NASA also performs).
It was sarcasm. The jobs in key congressional districts would disappear if NASA was allowed to do what makes sense for an effective space exploration program. So congress has taken over mandating what NASA's goals should be, to make sure that their key constituents remain employed on government contracts.
