If we can put a man on the moon, why can't we design a passenger airplane where we can carry all of our baggage on board?

Why has no airline or airplane manufacturer worked on this? Even if a bit of space was wasted, think of how much money carriers would save if they didn't have to maintain an outmoded, labor intensive baggage check system. And how much happier most all passengers would be, knowing their bags were guaranteed to be travelling with them.